tag:theconversation.com,2011:/africa/topics/aurora-borealis-14790/articlesAurora borealis – The Conversation2023-08-14T18:42:58Ztag:theconversation.com,2011:article/2099552023-08-14T18:42:58Z2023-08-14T18:42:58ZThis solar cycle, the sun’s activity is more powerful and surprising than predicted<figure><img src="https://images.theconversation.com/files/541795/original/file-20230808-15-85ytq4.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C1920%2C1080&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A coronal mass ejection on the solar surface.</span> <span class="attribution"><span class="source">(NASA/GSFC/SDO)</span></span></figcaption></figure><iframe style="width: 100%; height: 100px; border: none; position: relative; z-index: 1;" allowtransparency="" allow="clipboard-read; clipboard-write" src="https://narrations.ad-auris.com/widget/the-conversation-canada/this-solar-cycle-the-suns-activity-is-more-powerful-and-surprising-than-predicted" width="100%" height="400"></iframe>
<p>What do you feel when you see the aurora? </p>
<p>Otherwise known as the northern or southern lights, an aurora is light emitted by upper atmospheric particles as they interact with energized ones <a href="https://superdarn.ca/tutorials-11">from the magnetosphere</a>.</p>
<p>It’s an awe-inspiring and otherworldly event that those living at high latitudes can experience often. In <a href="https://creeliteracy.org/2018/05/01/northern-lights-creesimonsays/">Cree and Ojibwe teachings</a>, the northern lights are ancestral spirits who remain and communicate from the sky. </p>
<p>To scientists, the aurora is an infinitely complex amalgamation of <a href="https://www.nasa.gov/ionosphere">ionospheric</a> dynamics, a manifestation of Earth’s intrinsic connection to the sun. To industry, it’s a risk factor.</p>
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<a href="https://images.theconversation.com/files/540229/original/file-20230731-17-9pbazi.jpg?ixlib=rb-1.1.0&rect=0%2C2%2C936%2C524&q=45&auto=format&w=1000&fit=clip"><img alt="green lights ribbon in the sky above powerlines" src="https://images.theconversation.com/files/540229/original/file-20230731-17-9pbazi.jpg?ixlib=rb-1.1.0&rect=0%2C2%2C936%2C524&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/540229/original/file-20230731-17-9pbazi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/540229/original/file-20230731-17-9pbazi.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/540229/original/file-20230731-17-9pbazi.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/540229/original/file-20230731-17-9pbazi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=425&fit=crop&dpr=1 754w, https://images.theconversation.com/files/540229/original/file-20230731-17-9pbazi.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=425&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/540229/original/file-20230731-17-9pbazi.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=425&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">The aurora borealis seen above the Saskatoon SuperDARN space weather radar.</span>
<span class="attribution"><span class="source">(A. Reimer)</span></span>
</figcaption>
</figure>
<h2>The Starlink destruction event</h2>
<p>In February 2022, <a href="https://www.bbc.com/news/world-60317806">SpaceX launched 49 Starlink internet satellites into a low-Earth orbit (LEO)</a>. This was the 36th Starlink launch that SpaceX had carried out, and one that they anticipated to go off without a hitch, just like the 35 before. </p>
<p>On launch day, a <a href="https://www.swpc.noaa.gov/phenomena/coronal-mass-ejections">coronal mass ejection</a> — a large burst of plasma expelled from the sun — struck Earth. It caused a geomagnetic storm in the atmosphere between around 100 and 500 kilometres in altitude, the target range for Starlink. </p>
<p>This event injected an immense amount of electromagnetic energy straight into Earth’s upper atmosphere. It produced <a href="https://www.youtube.com/watch?v=q_GYySXTtio">beautiful auroral displays</a>, but the energy also increased the density of the air. A higher air density typically isn’t a big deal for LEO satellites, because it’s already extremely low at usual operational altitudes (upwards of 400 kilometres). </p>
<p>Starlink, however, was initially <a href="https://doi.org/10.1029/2022SW003074">launched into an altitude of 210 kilometres</a>. That’s much closer to Earth, with an exponentially higher air density. Thirty-eight out of those 49 initial launch satellites were subsequently lost due to atmospheric drag from the dense atmosphere, <a href="https://doi.org/10.1051/swsc/2022034">pulling them back to Earth</a>.</p>
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<figcaption><span class="caption">Starlink satellites burning up in the atmosphere over Puerto Rico, Feb. 7, 2022.</span></figcaption>
</figure>
<h2>Surprising solar cycle</h2>
<p>The sun undergoes a cycle — an 11-year one, to be exact — from which its activity increases and decreases periodically. At the peak of a cycle, we see more sunspots on the solar surface, more radiation emitted, and more solar flares. Geomagnetic storms like the one that caused the Starlink destruction event are a relatively common occurrence, especially when the sun reaches the peak of its 11-year cycle of strengthening and weakening activity. </p>
<p>In the previous cycle, which ended in 2019 (the 24th tracked cycle since 1755), <a href="https://doi.org/10.1016/j.asr.2022.10.033">there were 927 storms classed as moderate or weak alone</a> — an average of one every five or so days. </p>
<p>We’re currently four years into solar cycle 25, but this one has already proven surprising. The maximum activity of the 25th cycle was predicted to occur in 2025, but solar activity has already exceeded that. This means we’ve been seeing more geomagnetic storms, more auroral displays (and at lower latitudes than usual) and, potentially, more hazardous conditions for LEO satellites.</p>
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<a href="https://images.theconversation.com/files/540308/original/file-20230731-23-cwg668.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A plotted graph showing solar cycle sunspots" src="https://images.theconversation.com/files/540308/original/file-20230731-23-cwg668.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/540308/original/file-20230731-23-cwg668.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=221&fit=crop&dpr=1 600w, https://images.theconversation.com/files/540308/original/file-20230731-23-cwg668.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=221&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/540308/original/file-20230731-23-cwg668.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=221&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/540308/original/file-20230731-23-cwg668.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=278&fit=crop&dpr=1 754w, https://images.theconversation.com/files/540308/original/file-20230731-23-cwg668.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=278&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/540308/original/file-20230731-23-cwg668.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=278&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Solar activity as the number of sunspots visible on the solar surface. The number of sunspots seen is already considerably higher than what is expected from the solar maximum, two years ahead of schedule.</span>
<span class="attribution"><a class="source" href="https://www.swpc.noaa.gov/products/solar-cycle-progression">(National Oceanic and Atmospheric Administration)</a></span>
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<h2>Space weather — the unseen force of nature</h2>
<p>If geomagnetic storms are so common, why don’t they cause more issues? <a href="https://www.maine.gov/mema/maine-prepares/preparedness-library/geomagnetic-storms">The reality is that they do</a>, but the consequences are much less obvious than satellites burning up in the atmosphere.</p>
<p>When space weather energy enters Earth’s upper atmosphere, for example, the ionospheric composition changes in addition to the air getting denser. High-frequency, or “shortwave,” radio communication depends on a predictable ionosphere to broadcast long distances. </p>
<p>Geomagnetic storms that affect ionospheric composition can cause <a href="https://doi.org/10.1029/2018SW002008">radio blackouts</a>, such as a <a href="https://www.space.com/x-class-solar-flare-radio-blackout-august-2023">disruption in North America on Aug. 7</a>. Even minor storms can cause the degradation of radio signals used in military and maritime systems, aviation communication or ham radio. </p>
<p>Extreme storms can cause radio blackouts lasting hours, and for an entire side of the globe. Storms that big can also cause more discernible problems, such as the nine-hour <a href="http://www.hydroquebec.com/learning/notions-de-base/tempete-mars-1989.html">electricity outage experienced by Hydro-Québec in 1989</a>.</p>
<h2>Space weather warning systems</h2>
<p>It’s not all doom and disintegrating rockets, however. We can detect when a solar flare leaves the surface of the sun and predict roughly when it will affect the Earth, giving forewarning to certain types of storms and <a href="https://www.aurorawatch.ca/">chances to see the aurora</a>.</p>
<p>For many storms however, there is very little or no predictive capability because it depends on how the Earth’s magnetic field interacts with the solar wind, which is harder to see. </p>
<p>Nowcasting — using real-time data to understand conditions as they occur — is one of our best tools. With instruments such as ground-based radar and magnetometers on satellites, <a href="https://doi.org/10.1029/2023GL103733">we can estimate the electromagnetic space weather energy entering the atmosphere almost instantaneously</a>. </p>
<p>As for why SpaceX lost satellites in February 2022 during a minor geomagnetic storm, that was just a matter of timing. The loss of the satellites, however, is a stunning reminder of the power of the universe we live in.</p><img src="https://counter.theconversation.com/content/209955/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Daniel Billett receives funding from the European Space Agency and the Natural Sciences and Engineering Research Council of Canada. </span></em></p>We’re currently a few years into the 25th studied solar cycle. An 11-year period of sun activity, this solar cycle is more active than previously expected.Daniel Billett, Postdoctoral Fellow in Space Physics, University of SaskatchewanLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2026182023-03-29T04:32:17Z2023-03-29T04:32:17ZWhat are auroras, and why do they come in different shapes and colours? Two experts explain<figure><img src="https://images.theconversation.com/files/518083/original/file-20230329-24-p4501h.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C3000%2C1998&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://unsplash.com/photos/LtnPejWDSAY">Lightscape / Unsplash</a></span></figcaption></figure><p>Over millennia, humans have observed and been inspired by beautiful displays of light bands dancing across dark night skies. Today, we call these lights the aurora: the aurora borealis in the northern hemisphere, and the aurora australis in the south.</p>
<p>Nowadays, we understand auroras are caused by charged particles from Earth’s magnetosphere and the solar wind colliding with other particles in Earth’s upper atmosphere. Those collisions excite the atmospheric particles, which then release light as they “relax” back to their unexcited state. </p>
<p>The colour of the light corresponds to the release of discrete chunks of energy by the atmospheric particles, and is also an indicator of how much energy was absorbed in the initial collision.</p>
<p>The frequency and intensity of auroral displays is related to activity on the Sun, which follows an 11-year cycle. Currently, we are approaching the next maximum, which is <a href="https://www.weather.gov/news/201509-solar-cycle">expected in 2025</a>.</p>
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<figcaption><span class="caption">Fox Fires, a short film inspired by the Finnish folk tale of the aurora borealis.</span></figcaption>
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<h2>Connections to the Sun</h2>
<p>Such displays have long been documented by peoples throughout <a href="http://www.ewebtribe.com/NACulture/articles/aurora.html">North America</a>, Europe, <a href="https://www.smithsonianmag.com/smart-news/evidence-of-earliest-candidate-aurora-found-in-ancient-chinese-texts-180979979/">Asia</a> and <a href="https://education.riaus.org.au/cosmos-magazine-aurora-traditions-of-the-first-australians/">Australia</a>.</p>
<p>In the 17th century, scientific explanations for what caused the aurora began to surface. Possible explanations included air from Earth’s atmosphere rising out of Earth’s shadow to become sunlit (<a href="https://www.nasa.gov/mission_pages/themis/auroras/aurora_history.html">Galileo in 1619</a>) and light reflections from high-altitude ice crystals (<a href="https://pwg.gsfc.nasa.gov/polar/EPO/auroral_poster/aurora_all.pdf">Rene Descartes and others</a>). </p>
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Read more:
<a href="https://theconversation.com/do-the-northern-lights-make-sounds-that-you-can-hear-168032">Do the northern lights make sounds that you can hear?</a>
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<p>In 1716, English astronomer Edmund Halley was the first to suggest a possible connection with Earth’s magnetic field. In 1731, a French philosopher named Jean-Jacques d'Ortous de Mairan noted a coincidence between the number of <a href="https://theconversation.com/giant-sunspot-returns-and-its-bigger-and-badder-than-ever-34002">sunspots</a> and aurora. He proposed that the aurora was connected with the Sun’s atmosphere. </p>
<p>It was here that the connection between activity on the Sun was linked with auroras here on Earth, giving rise to the areas of science now called “<a href="https://www.nasa.gov/mission_pages/sunearth/the-heliopedia">heliophysics</a>” and “<a href="https://spaceplace.nasa.gov/spaceweather/en/">space weather</a>”.</p>
<h2>Earth’s magnetic field as a particle trap</h2>
<p>The most common source of <a href="https://media.bom.gov.au/social/blog/1557/what-is-an-aurora/#:%7E:text=The%20colour%20emitted%20depends%20on,dark%20red%20or%20blue%20light.">aurora</a> is particles travelling within Earth’s <a href="https://www.nasa.gov/mission_pages/sunearth/multimedia/magnetosphere.html">magnetosphere</a>, the region of space occupied by Earth’s natural magnetic field. </p>
<p>Images of Earth’s magnetosphere typically show how the magnetic field “bubble” protects Earth from space radiation and repels most disturbances in the solar wind. However, what is not normally highlighted is the fact that Earth’s magnetic field contains its own population of electrically charged particles (or “plasma”). </p>
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<figcaption><span class="caption">Model representation of Earth’s magnetic field interacting with the solar wind.</span></figcaption>
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<p>The magnetosphere is composed of charged particles that have escaped from Earth’s upper atmosphere and charged particles that have entered from the solar wind. Both types of particles are trapped in Earth’s magnetic field.</p>
<p>The motions of electrically charged particles are controlled by electric and magnetic fields. Charged particles gyrate around magnetic field lines, so when viewed at large scales magnetic field lines act as “pipelines” for charged particles in a plasma.</p>
<p>The Earth’s magnetic field is similar to a standard “dipole” magnetic field, with field lines bunching together near the poles. This bunching up of field lines actually alters the particle trajectories, effectively turning them around to go back the way they came, in a process called “magnetic mirroring”.</p>
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<figcaption><span class="caption">‘Magnetic mirroring’ makes charged particles bounce back and forth between the poles.</span></figcaption>
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<h2>Earth’s magnetosphere in a turbulent solar wind</h2>
<p>During quiet and stable conditions, most particles in the magnetosphere stay trapped, happily bouncing between the south and north magnetic poles out in space. However, if a disturbance in the solar wind (such as a <a href="https://www.swpc.noaa.gov/phenomena/coronal-mass-ejections">coronal mass ejection</a>) gives the magnetosphere a “whack”, it becomes disturbed. </p>
<p>The trapped particles are accelerated and the magnetic field “pipelines” suddenly change. Particles that were happily bouncing between north and south now have their bouncing location moved to lower altitudes, where Earth’s atmosphere becomes more dense.</p>
<p>As a result, the charged particles are now likely to collide with atmospheric particles as they reach the polar regions. This is called “particle precipitation”. Then, when each collision occurs, energy is transferred to the atmospheric particles, exciting them. Once they relax, they emit the light that forms the beautiful aurora we see.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1640474775754784768"}"></div></p>
<h2>Curtains, colours and cameras</h2>
<p>The amazing displays of aurora dancing across the sky are the result of the complex interactions between the <a href="https://www.nasa.gov/feature/goddard/2021/themis-researchers-find-standing-waves-at-edge-of-earth-magnetic-bubble">solar wind and the magnetosphere</a>. </p>
<p>Aurora appearing, disappearing, brightening and forming structures like curtains, swirls, picket fences and travelling waves are all visual representations of the invisible, ever-changing dynamics in Earth’s magnetosphere as it interacts with the solar wind.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1640084831668432896"}"></div></p>
<p>As these videos show, aurora comes in all sorts of <a href="https://aurorasaurus.org/learn#aurora-colors">colours</a>. </p>
<p>The most common are the greens and reds, which are both emitted by oxygen in the upper atmosphere. Green auroras correspond to altitudes close to 100 km, whereas the red auroras are higher up, above 200 km. </p>
<p>Blue colours are emitted by nitrogen – which can also emit some reds. A range of pinks, purples and even white light are also possible due to a mixture of these emissions.</p>
<p>The aurora is more brilliant in photographs because camera sensors are more sensitive than the human eye. Specifically, our eyes are less sensitive to colour at night. However, if the aurora is bright enough it can be quite a sight for the naked eye. </p>
<h2>Where and when?</h2>
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<figcaption><span class="caption">Catching aurora in the southern hemisphere.</span></figcaption>
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<p>Even under quiet space weather conditions, aurora can be very prominent at high latitudes, such as in <a href="https://allsky.gi.alaska.edu/">Alaska</a>, <a href="https://auroramax.com/live">Canada</a>, <a href="https://site.uit.no/spaceweather/data-and-products/tgo-all-sky-cameras/">Scandinavia</a> and <a href="http://polaris.nipr.ac.jp/%7Eacaurora/syoCDC/index.html">Antarctica</a>. When a space weather disturbance takes place, auroras can migrate to much lower latitudes to become visible across the continental <a href="https://www.youtube.com/watch?v=_Myo-0CLrck&t=2s">United States</a>, <a href="https://www.agenzianova.com/en/news/aurora-boreale-in-germania-video/">central Europe</a> and even <a href="https://twitter.com/Rosiebscorpio/status/1639180442053283840?s=20">southern</a> and <a href="https://twitter.com/perthobs/status/1639122431532216325?s=20">mainland Australia</a>. </p>
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<p>The severity of the space weather event typically controls the range of locations where the aurora is visible. The strongest events are the most rare.</p>
<p>So, if you’re interested in hunting auroras, keep an eye on your local space weather forecasts (<a href="https://www.swpc.noaa.gov/">US</a>, <a href="https://www.sws.bom.gov.au/">Australia</a>, <a href="https://www.metoffice.gov.uk/weather/specialist-forecasts/space-weather">UK</a>, <a href="https://spaceweather.sansa.org.za/">South Africa</a> and <a href="https://swe.ssa.esa.int/current-space-weather">Europe</a>). There are also numerous space weather experts on social media and even aurora-hunting citizen science projects (such as <a href="https://www.aurorasaurus.org/">Aurorasaurus</a>) that you can contribute towards!</p>
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<figcaption><span class="caption">A rare sighting of the aurora australis from central Australia, with Uluru in the foreground.</span></figcaption>
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<p>Get outside and witness one of nature’s true natural beauties – aurora, Earth’s gateway to the heavens.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/fire-in-the-sky-the-southern-lights-in-indigenous-oral-traditions-39113">Fire in the sky: The southern lights in Indigenous oral traditions</a>
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<img src="https://counter.theconversation.com/content/202618/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Brett Carter receives funding from the Australian Research Council, the SmartSat CRC and the Australian Department of Defence. He has also consulted for Chimu Adventures as part of their Southern Lights Flight tours. </span></em></p><p class="fine-print"><em><span>Elizabeth A. MacDonald receives funding from NASA and employed by NASA's Goddard Space Flight Center. The Aurorasaurus project receives funding from NASA and NSF. </span></em></p>The aurora is one of nature’s most spectacular sights, a dazzling glow in the upper atmosphere driven by space weather.Brett Carter, Associate Professor, RMIT UniversityElizabeth A. MacDonald, Space Physicist, NASALicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2007772023-03-03T12:19:06Z2023-03-03T12:19:06ZThe northern lights appeared in southern England twice in one week - here’s why this could happen again soon<figure><img src="https://images.theconversation.com/files/513215/original/file-20230302-21-6rlu6d.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C5472%2C3563&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The northern lights seen in the south of the UK weren't quite as vivid as the kind of displays seen closer to the polar regions</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/aurora-borealis-silhouette-love-romantic-couple-1247862049">basiczto/Shutterstock</a></span></figcaption></figure><p>People across the UK, <a href="https://www.theguardian.com/travel/2023/feb/27/northern-lights-dazzle-across-scotland-ireland-and-south-through-england">from the Shetland Islands to Somerset</a> and from Norfolk to Northern Ireland, have been treated to a stunning display of the aurora borealis or northern lights recently. But what causes this beautiful phenomena and why has it appeared so far south?</p>
<p>For thousands of years, people associated the ghostly northern lights with the <a href="https://www.telegraph.co.uk/travel/comment/Northern-Lights-celestial-dancers-or-the-souls-of-fallen-warriors/">world of restless spirits</a>. But over the last century, science has revealed that aurorae originate in the area surrounding our planet. The near-Earth region of space is <a href="https://science.nasa.gov/heliophysics/focus-areas/magnetosphere-ionosphere#:%7E:text=A%20magnetosphere%20is%20the%20region,role%20in%20our%20planet's%20habitability.">known as the magnetosphere</a>. It is a cocktail of atoms and molecules from the Earth’s upper atmosphere, shattered and heated by <a href="https://www.swpc.noaa.gov/phenomena/solar-euv-irradiance">solar radiation</a> (electromagnetic radiation emitted by the Sun).</p>
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<p>The <a href="https://www.nasa.gov/aurora">aurora borealis</a> is created when these electrically charged particles rain down into the upper atmosphere. Most of the incoming particles that stimulate the light are electrons. As the patterns of precipitation shift, the aurora shimmer and dance across the sky. Electrons are accelerated down along the Earth’s magnetic field towards the polar regions. </p>
<p>The Sun emits a <a href="https://slate.com/technology/2014/07/solar-wind-versus-fusion-how-does-the-sun-lose-mass.html">couple of million tonnes of particles every second</a>, forming the <a href="https://www.space.com/22215-solar-wind.html">solar wind</a> that constantly flows through our solar system. The solar wind drags remnants of the Sun’s powerful magnetic field with it, bathing the planets in a magnetised steam of particles smaller than atoms. Interactions between the solar wind and the Earth’s magnetosphere power the northern lights. </p>
<p>So what happened this week to drive aurorae to much lower latitudes than normal?</p>
<p>Towards the end of last week, scientists noticed a pair of <a href="https://www.jpl.nasa.gov/nmp/st5/SCIENCE/cme.html#:%7E:text=Coronal%20mass%20ejections%20(CMEs)%20are,scientists%20call%20%22flux%20rope.%22">coronal mass ejections</a> (CMEs) on the Sun. A CME is an eruption of material from the Sun’s outer atmosphere (the corona). These explosive bursts can launch billions of tonnes of material in almost any direction, and Earth is typically hit a couple of times per month. As it happens, this pair of CMEs both fired Earthward, with the first leaving the Sun late on February 24 and the second late on February 25. </p>
<p>Travelling at about 3 million kilometres per hour, the first CME took about 48 hours to travel the 150 million kilometres to Earth and slammed into the magnetosphere around 7pm (UK time) on Sunday, February 26. The impact of a billion tonnes of highly magnetised, electrically charged material triggered a geomagnetic storm (a major disturbance of the Earth’s magnetosphere). Electrons in the magnetosphere accelerated into Earth’s atmosphere, sparking intense auroral displays that rapidly expanded much further towards the equator than usual.</p>
<p>Timing was key. The geomagnetic storm happened in the early evening in the UK. Although dark, most people were awake and the weather was fine with clear skies over most of the country. As the geomagnetic storm intensified over the next few hours, pictures of the aurora from as far south as Kent filled social media timelines, no doubt prompting more people to scan the skies.</p>
<p>Had the CME arrived a few hours later, most people in the UK would have been in bed and probably missed the event. Cloudy weather would have obscured the show. But the timing was right and the famously unpredictable UK weather was cooperating (for once).</p>
<p>By late Sunday evening, my phone was ringing. As a space scientist who researches the connections between the Sun and Earth, I’m often contacted by the media when there is an auroral display over the UK. </p>
<p>As Monday morning broke, most of the media were running with stories of the previous night’s display. Sure enough, most channels had found expert talking heads to talk about the science. But for me, this event was different. Normally, “morning after” media work involves answering an inevitable question.</p>
<p>“Will we see the northern lights again tonight?”</p>
<p>Usually, the answer is “probably not”. In most cases, after 24 hours the intensity of a geomagnetic storm has waned and the northern lights retreat away from the UK towards their usual location at the edge of the arctic circle. </p>
<p>But this time, things were different. The second CME launched towards the Earth was still in transit, so it was a rare opportunity for me to give an optimistic prediction. The second CME arrived in the wake of the first and caught Earth with a glancing blow around lunchtime on Monday, February 27. The weather conditions in the UK had deteriorated and many hopeful aurora chasers were thwarted by cloud. But geomagnetic activity remained high for a second night running and folks with cloud-free skies were treated to another display of the northern lights. </p>
<p>When will we next <a href="https://aurorawatch.lancs.ac.uk/">see them over the UK</a>? It’s hard to say, but the prospects are improving. The Sun’s activity varies over an 11-year <a href="https://www.space.com/solar-cycle-frequency-prediction-facts">solar cycle</a>, with CMEs (and aurora over the UK) more likely during the active parts of the cycle. At present, solar activity is increasing as we move towards the next solar maximum, expected in 2025. <a href="http://www.geomag.bgs.ac.uk/education/viewing_aurora.html">Keep watching the skies</a> – and social media.</p><img src="https://counter.theconversation.com/content/200777/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jim Wild receives funding from UK Research and Innovation (UKRI) that supports his research at Lancaster University.</span></em></p>People expect to brave brutally cold landscapes if they want to catch sight of the aurora borealis. So people were stunned to see the ethereal light display as far south as Cornwall.Jim Wild, Professor of Space Physics, Lancaster UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1775102022-03-02T13:28:17Z2022-03-02T13:28:17ZSolar storms can destroy satellites with ease – a space weather expert explains the science<figure><img src="https://images.theconversation.com/files/448971/original/file-20220228-13-1r7fc0y.jpg?ixlib=rb-1.1.0&rect=0%2C42%2C4096%2C4046&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The Sun occasionally ejects large amounts of energy and particles into space that can smash into Earth.</span> <span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Coronal_mass_ejection_erupts_on_the_Sun,_31_August_2012.jpg#/media/File:Coronal_mass_ejection_erupts_on_the_Sun,_31_August_2012.jpg">NASA/GSFC/SDO via WikimediaCommons</a></span></figcaption></figure><p>On Feb. 4, 2022, SpaceX launched 49 satellites as part of Elon Musk’s Starlink internet project, <a href="https://www.cnbc.com/2022/02/09/spacex-losing-starlink-satellites-due-to-geomagnetic-space-storm.html">most of which burned up in the atmosphere days later</a>. The cause of this more than <a href="https://www.cnbc.com/2022/02/09/spacex-losing-starlink-satellites-due-to-geomagnetic-space-storm.html">US$50 million</a> failure was a geomagnetic storm caused by the Sun. </p>
<p>Geomagnetic storms occur when space weather hits and interacts with the Earth. Space weather is caused by fluctuations within the Sun that blast electrons, protons and other particles into space. <a href="https://scholar.google.com/citations?user=TdViV_sAAAAJ&hl=en&oi=ao">I study the hazards space weather poses to space-based assets</a> and how scientists can improve the models and prediction of space weather to protect against these hazards. </p>
<p>When space weather reaches Earth, it triggers many complicated processes that can cause a lot of trouble for anything in orbit. And engineers like me are working to better understand these risks and defend satellites against them.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/lOgIrDirDYY?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">The Sun occasionally blasts huge amounts of particles into space during active events like solar flares and coronal mass ejections.</span></figcaption>
</figure>
<h2>What causes space weather?</h2>
<p>The Sun is always releasing a steady amount of charged particles into space. This is called the solar wind. Solar wind also carries with it the solar magnetic field. Sometimes, localized fluctuations on the Sun will <a href="https://www.swpc.noaa.gov/phenomena/solar-wind">hurl unusually strong bursts of particles in a particular direction</a>. If Earth happens to be in the path of the enhanced solar wind generated by one of these events and gets hit, you get a geomagnetic storm.</p>
<p>The two most common causes of geomagnetic storms are <a href="https://www.swpc.noaa.gov/phenomena/coronal-mass-ejections">coronal mass ejections</a> – explosions of plasma from the surface of the Sun – and <a href="https://www.swpc.noaa.gov/news/coronal-hole-high-speed-streams-ch-hss">solar wind that escapes through coronal holes</a> – spots of low density in the Sun’s outer atmosphere.</p>
<p>The speed at which the ejected plasma or solar wind arrives at Earth is an important factor – the faster the speed, the stronger the geomagnetic storm. Normally, <a href="https://pwg.gsfc.nasa.gov/istp/nicky/cme-chase.html#:%7E:text=Near%20solar%20activity%20maximum%2C%20the,about%20400%20kilometers%20per%20second">solar wind travels at roughly 900,000 mph</a> (1.4 million kph). But strong solar events can release winds up to five times as fast.</p>
<p>The strongest geomagnetic storm on record was caused by a <a href="https://www.history.com/news/a-perfect-solar-superstorm-the-1859-carrington-event">coronal mass ejection in September 1859</a>. When the mass of particles hit Earth, they caused electrical surges in telegraph lines that shocked operators and, in some extreme cases, <a href="https://doi.org/10.1016/j.asr.2006.01.013">actually set telegraph instruments on fire</a>. Research suggests that if a geomagnetic storm of this magnitude hit Earth today, it would cause roughly <a href="https://www.history.com/news/a-perfect-solar-superstorm-the-1859-carrington-event">$2 trillion in damage</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/448952/original/file-20220228-15-qnx8er.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A drawing showing the Earth surrounded by a magnetic field with solar energy compressing one side." src="https://images.theconversation.com/files/448952/original/file-20220228-15-qnx8er.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/448952/original/file-20220228-15-qnx8er.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=328&fit=crop&dpr=1 600w, https://images.theconversation.com/files/448952/original/file-20220228-15-qnx8er.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=328&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/448952/original/file-20220228-15-qnx8er.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=328&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/448952/original/file-20220228-15-qnx8er.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=412&fit=crop&dpr=1 754w, https://images.theconversation.com/files/448952/original/file-20220228-15-qnx8er.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=412&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/448952/original/file-20220228-15-qnx8er.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=412&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The Earth’s magnetic field acts as a shield that absorbs most solar wind.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Magnetosphere_rendition.jpg#/media/File:Magnetosphere_rendition.jpg">NASA via WikimediaCommons</a></span>
</figcaption>
</figure>
<h2>A magnetic shield</h2>
<p>Emissions from the Sun, including the solar wind, would be incredibly dangerous to any life form unlucky enough to be directly exposed to them. Thankfully, Earth’s magnetic field does a lot to protect humanity.</p>
<p>The first thing solar wind hits as it approaches Earth is the magnetosphere. This region surrounding the Earth’s atmosphere is filled with plasma made of electrons and ions. It’s dominated by the planet’s strong magnetic field. When solar wind hits the magnetosphere, it transfers mass, energy and momentum into this layer. </p>
<p>The magnetosphere can absorb most of the energy from the everyday level of solar wind. But during strong storms, it can get overloaded and transfer excess energy to the upper layers of Earth’s atmosphere near the poles. This redirection of energy to the poles is what <a href="https://www.swpc.noaa.gov/phenomena/aurora">results in fantastic aurora events</a>, but it also causes changes in the upper atmosphere that can harm space assets.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/449002/original/file-20220228-15-1ec6d9h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A diagram showing the many layers of the atmosphere: the troposphere, from 0 to 12 km from Earth's surface, moving upward through the stratosphere, mesosphere, thermosphere and finally the exosphere, the layer from 700 to 190,000 km above Earth." src="https://images.theconversation.com/files/449002/original/file-20220228-15-1ec6d9h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/449002/original/file-20220228-15-1ec6d9h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=500&fit=crop&dpr=1 600w, https://images.theconversation.com/files/449002/original/file-20220228-15-1ec6d9h.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=500&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/449002/original/file-20220228-15-1ec6d9h.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=500&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/449002/original/file-20220228-15-1ec6d9h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=628&fit=crop&dpr=1 754w, https://images.theconversation.com/files/449002/original/file-20220228-15-1ec6d9h.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=628&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/449002/original/file-20220228-15-1ec6d9h.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=628&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The different layers of Earth’s atmosphere are all affected by solar storms differently.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/illustration/cartoon-atmosphere-layers-card-poster-royalty-free-illustration/1064199092?adppopup=true">Bigmouse108 / iStock via Getty Images</a></span>
</figcaption>
</figure>
<h2>Dangers to what’s in orbit</h2>
<p>There a few different ways geomagnetic storms threaten orbiting satellites that serve people on the ground daily.</p>
<p>When the atmosphere absorbs energy from magnetic storms, it heats up and expands upward. This <a href="https://doi.org/10.1029/2005JA011274">expansion significantly increases the density of the thermosphere</a>, the layer of the atmosphere that extends from about 50 miles (80 kilometers) to roughly 600 miles (1,000 km) above the surface of the Earth. Higher density means <a href="https://www.swpc.noaa.gov/impacts/satellite-drag#:%7E:text=The%20drag%20force%20on%20satellites,were%20previously%20at%20lower%20altitudes">more drag, which can be a problem for satellites</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/448968/original/file-20220228-13-1wlbbd7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A satellite carrying a stack of Starlink satellites." src="https://images.theconversation.com/files/448968/original/file-20220228-13-1wlbbd7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/448968/original/file-20220228-13-1wlbbd7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/448968/original/file-20220228-13-1wlbbd7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/448968/original/file-20220228-13-1wlbbd7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/448968/original/file-20220228-13-1wlbbd7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/448968/original/file-20220228-13-1wlbbd7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/448968/original/file-20220228-13-1wlbbd7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Starlink satellites are released in batches, and 40 were destroyed in early February because of a geomagnetic storm.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Starlink_Mission_(47926144123).jpg#/media/File:Starlink_Mission_(47926144123).jpg">SpaceX via WikimediaCommons</a></span>
</figcaption>
</figure>
<p>This situation is exactly what led to the demise of the the SpaceX Starlink satellites in February. Starlink satellites are <a href="https://www.cnbc.com/2022/02/09/spacex-losing-starlink-satellites-due-to-geomagnetic-space-storm.html">dropped off by Falcon 9 rockets into a low-altitude orbit</a>, typically somewhere between 60 and 120 miles (100 and 200 km) above the Earth’s surface. The satellites then use onboard engines to slowly overcome the force of drag and raise themselves to their final altitude of approximately <a href="https://www.cnbc.com/2022/02/09/spacex-losing-starlink-satellites-due-to-geomagnetic-space-storm.html">350 miles (550 km)</a>. </p>
<p>The latest batch of Starlink satellites encountered a geomagnetic storm while still in very low-Earth orbit. Their engines could not overcome the <a href="https://www.cnbc.com/2022/02/09/spacex-losing-starlink-satellites-due-to-geomagnetic-space-storm.html">significantly increased drag</a>, and the satellites began slowly falling toward Earth and eventually burned up in the atmosphere.</p>
<p>Drag is just one hazard that space weather poses to space-based assets. The significant increase in high-energy electrons within the magnetosphere during strong geomagnetic storms means more electrons will penetrate the shielding on a spacecraft and accumulate within its electronics. This buildup of electrons can <a href="https://www.nasa.gov/vision/universe/solarsystem/killer_electrons.html">discharge in what is basically a small lightning strike</a> and damage electronics. </p>
<p>Penetrating radiation or charged particles in the magnetosphere – even during mild geomagnetic storms – can also <a href="https://www.cambridge.org/core/books/spacecraftenvironment-interactions/F722691656610F887D25CB66695DDE01#:%7E:text=Spacecraft%2DEnvironment%20Interactions%20is%20a,and%20for%20spacecraft%20system%20engineers">alter the output signal from electronic devices</a>. This phenomenon can cause errors in any part of a spacecraft’s electronics system, and if the error occurs in something critical, the entire satellite can fail. Small errors are common and usually fixable, but <a href="https://doi.org/10.1002/swe.20023">total failures, though rare, do happen</a>.</p>
<p>Finally, geomagnetic storms can disrupt the ability of satellites to communicate with Earth using radio waves. Many communications technologies, like GPS, for example, <a href="https://www.sciencedirect.com/topics/social-sciences/radio-waves#:%7E:text=GPS%20receivers%20use%20radio%20waves,a%20reference%20system%20for%20GPS.">rely on radio waves</a>. The atmosphere always <a href="https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=6431636">distorts radio waves by some amount </a>, so engineers correct for this distortion when building communication systems. But during geomagnetic storms, changes in the ionosphere – the charged equivalent of the thermosphere that spans roughly the same altitude range – will change how radio waves travel through it. The calibrations in place for a quiet atmosphere become wrong during geomagnetic storms.</p>
<p>This, for example, makes it difficult to lock onto GPS signals and can <a href="https://doi.org/10.1029/2018SW001940">throw off the positioning by a few meters</a>. For many industries – aviation, maritime, robotics, transportation, farming, military and others – GPS positioning errors of a few meters are simply not tenable. Autonomous driving systems will require accurate positioning as well.</p>
<h2>How to protect against space weather</h2>
<p>Satellites are critically important for much of the modern world to function, and protecting space assets from space weather is an <a href="https://www.sworm.gov/">important area of research</a>. </p>
<p>Some of the risks can be minimized by <a href="https://doi.org/10.1038/s41598-021-99739-2">shielding electronics from radiation</a> or <a href="https://doi.org/10.1016/j.actaastro.2020.12.010">developing materials</a> that are more resistant to radiation. But there is only so much shielding that can be done in the face of a <a href="https://doi.org/10.1038/s41598-021-99739-2">powerful geomagnetic storm</a>.</p>
<p>[<em>Over 140,000 readers rely on The Conversation’s newsletters to understand the world.</em> <a href="https://memberservices.theconversation.com/newsletters/?source=inline-140ksignup">Sign up today</a>.]</p>
<p>The ability to accurately forecast storms would make it possible to preemptively safeguard satellites and other assets to a certain extent by shutting down sensitive electronics or reorienting the satellites to be better protected. But while the modeling and forecasting of geomagnetic storms has significantly improved over the past few years, the projections are often wrong. The National Oceanic and Atmospheric Administration had warned that, following a coronal mass ejection, a <a href="https://www.space.com/sunspot-ar2936-solar-flare-cme-arrival-earth">geomagnetic storm was “likely” to occur</a> the day before or the day of the February Starlink launch. The mission went ahead anyway.</p>
<p>The Sun is like a child that often throws tantrums. It’s essential for life to go on, but its ever-changing disposition make things challenging.</p><img src="https://counter.theconversation.com/content/177510/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Piyush Mehta receives funding from the National Science Foundation and the National Aeronautics and Space Administration. He is affiliated with the National Aeronautics and Space Administration as a Special Government Employee and is a member of the NASA Space Weather Council. </span></em></p>Space weather can affect satellites in a number of different ways, from frying electronics to increasing drag in the atmosphere.Piyush Mehta, Assistant Professor of Mechanical and Aerospace Engineering, West Virginia UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1740192022-01-20T15:17:36Z2022-01-20T15:17:36ZAre the northern lights caused by ‘particles from the Sun’? Not exactly<figure><img src="https://images.theconversation.com/files/440264/original/file-20220111-23-19p1ssc.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C5406%2C3599&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/northern-lights-on-night-sky-aurora-1908662476">PhotoVisions/Shutterstock</a></span></figcaption></figure><p>What a spectacle a big aurora is, its shimmering curtains and colourful rays of light illuminating a dark sky. Many people refer to aurora as the northern lights (the aurora borealis), but there are <a href="https://www.nationalgeographic.co.uk/travel/2020/05/electric-dreams-where-to-see-the-southern-lights">southern lights</a> too (the aurora australis). Either way, if you’re lucky enough to catch a glimpse of this phenomenon, it’s something you won’t soon forget.</p>
<p>The aurora is <a href="https://link.springer.com/article/10.1007%2Fs11214-021-00798-8">often explained simply</a> as “particles from the Sun” hitting our atmosphere. But that’s not technically accurate except in a few limited cases. So <a href="https://www.skyatnightmagazine.com/space-science/what-causes-northern-lights/">what does happen</a> to create this <a href="https://www.nasa.gov/aurora">natural marvel</a>?</p>
<p>We see the aurora when energetic charged particles – electrons and sometimes ions – collide with atoms in the upper atmosphere. While the aurora often follows explosive events on the Sun, it’s not quite true to say these energetic particles that cause the aurora come from the Sun.</p>
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Read more:
<a href="https://theconversation.com/curious-kids-what-causes-the-northern-lights-111573">Curious Kids: what causes the northern lights?</a>
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<p>Earth’s magnetism, the force that directs the compass needle, dominates the motions of electrically charged particles in space around Earth. The <a href="https://www.feynmanlectures.caltech.edu/II_01.html#Ch1-S2">magnetic field</a> near the surface of Earth is normally steady, but its strength and direction fluctuate when there are displays of the aurora. These fluctuations are caused by what’s called a magnetic substorm – a rapid disturbance in the magnetic field in near-Earth space.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/440886/original/file-20220114-23-1o904tp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/440886/original/file-20220114-23-1o904tp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=365&fit=crop&dpr=1 600w, https://images.theconversation.com/files/440886/original/file-20220114-23-1o904tp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=365&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/440886/original/file-20220114-23-1o904tp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=365&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/440886/original/file-20220114-23-1o904tp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=459&fit=crop&dpr=1 754w, https://images.theconversation.com/files/440886/original/file-20220114-23-1o904tp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=459&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/440886/original/file-20220114-23-1o904tp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=459&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Many people travel to high-latitude countries every year in the hope of seeing the northern lights.</span>
<span class="attribution"><span class="source">Douglas Cooper</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>To understand what happens to trigger a substorm, we first need to learn about plasma. Plasma is a gas in which a significant number of the atoms have been broken into ions and electrons. The gas of the uppermost regions of Earth’s atmosphere is in the plasma state, as is the gas that makes up the Sun and other stars. A gas of plasma flows away continuously from the Sun: this is called the <a href="https://www.jpl.nasa.gov/nmp/st5/SCIENCE/solarwind.html">solar wind</a>.</p>
<p>Plasma behaves differently from those gases we meet in everyday life. Wave a magnet around in your kitchen and nothing much happens. The air of the kitchen consists overwhelmingly of electrically neutral atoms, so it’s quite undisturbed by the moving magnet. In a plasma, however, with its electrically charged particles, things are different. So if your house was filled with plasma, waving a magnet around would make the air move.</p>
<p>When solar wind plasma arrives at the earth it interacts with the planet’s magnetic field (as illustrated below – the magnetic field is represented by the lines that look a bit like a spider). Most of the time, plasma travels easily along the lines of the magnetic field, but not across them. This means that solar wind arriving at Earth is diverted around the planet and kept away from the Earth’s atmosphere. In turn, the solar wind drags the field lines out into the elongated form seen on the night side, called the magnetotail.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/440887/original/file-20220114-27-1lpyj1p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/440887/original/file-20220114-27-1lpyj1p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=469&fit=crop&dpr=1 600w, https://images.theconversation.com/files/440887/original/file-20220114-27-1lpyj1p.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=469&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/440887/original/file-20220114-27-1lpyj1p.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=469&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/440887/original/file-20220114-27-1lpyj1p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=589&fit=crop&dpr=1 754w, https://images.theconversation.com/files/440887/original/file-20220114-27-1lpyj1p.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=589&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/440887/original/file-20220114-27-1lpyj1p.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=589&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A coronal mass ejection leaves the Sun, travelling towards the Earth’s magnetic field (this image is not to scale).</span>
<span class="attribution"><a class="source" href="https://sohowww.nascom.nasa.gov/gallery/images/large/sunearth01_prev.jpg">SOHO (ESA & NASA)</a></span>
</figcaption>
</figure>
<p>Sometimes moving plasma brings magnetic fields from different regions together, causing a local breakdown in the pattern of magnetic field lines. This phenomenon, called <a href="https://www.nasa.gov/content/goddard/science-of-magnetic-reconnection">magnetic reconnection</a>, heralds a new magnetic configuration, and, importantly, unleashes a huge amount of energy. </p>
<p>These events happen fairly often in the Sun’s outer atmosphere, causing an explosive energy release and pushing clouds of magnetised gas, called coronal mass ejections, away from the Sun (as seen in the image above).</p>
<p>If a coronal mass ejection arrives at Earth it can in turn trigger reconnection in the magnetotail, releasing energy that drives electrical currents in near-Earth space: the substorm. Strong <a href="https://link.springer.com/article/10.1007%2Fs11214-008-9373-9">electric fields</a> that develop in this process accelerate electrons to high energies. Some of these electrons may have come from the solar wind, allowed into near-Earth space by reconnection, but their acceleration in the substorm is essential to their role in the aurora.</p>
<p>These particles are then funnelled by the magnetic field towards the atmosphere high above the polar regions. There they collide with the oxygen and nitrogen atoms, exciting them <a href="http://wp.lancs.ac.uk/aurorawatchuk/2017/05/10/the-vivid-lights-what-causes-the-colour-of-the-aurora/">to glow</a> as the aurora.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/northern-lights-to-death-rays-how-electromagnetism-haunts-our-everyday-life-85129">Northern lights to death rays: how electromagnetism haunts our everyday life</a>
</strong>
</em>
</p>
<hr>
<p>Now you know exactly what causes the northern lights, how do you optimise your chances of seeing it? Seek out dark skies far from cities and towns. The further north you can go the better but you don’t need to be in the Arctic Circle. We see them from time to time in Scotland, and they’ve even been spotted in the <a href="https://www.bbc.co.uk/news/uk-england-tyne-59929434">north of England</a> – although they’re still better seen at higher latitudes.</p>
<p>Websites such as <a href="https://aurorawatch.lancs.ac.uk/">AuroraWatch UK</a> can tell you when it’s worth heading outside. And remember that while <a href="http://sidc.oma.be/">events on the Sun</a> can give us a few days warning, these are indicative, not foolproof. Perhaps part of the magic lies in the fact that you need a little bit of luck to see the aurora in all its glory.</p><img src="https://counter.theconversation.com/content/174019/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Alexander MacKinnon has previously received funding from the STFC, for research on energetic phenomena on the Sun.</span></em></p>It’s often said that the aurora, or the northern lights, is caused by ‘particles from the Sun’. But in reality things are more complicated.Alexander MacKinnon, Honorary Research Fellow, Physics and Astronomy, University of GlasgowLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1650002021-10-21T19:12:08Z2021-10-21T19:12:08ZCurious Kids: Why are the northern lights only spotted near the North Pole?<figure><img src="https://images.theconversation.com/files/427864/original/file-20211021-15-1x7qi1g.jpg?ixlib=rb-1.1.0&rect=0%2C12%2C8075%2C2864&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The Aurora Australis, or Southern Lights, reflected in the water.</span> <span class="attribution"><span class="source">(Shutterstock)</span></span></figcaption></figure><figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=293&fit=crop&dpr=1 600w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=293&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=293&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=368&fit=crop&dpr=1 754w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=368&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=368&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
</figcaption>
</figure>
<p><em>Curious Kids is a series for children of all ages. Have a question you’d like an expert to answer? Send it to <a href="mailto:curiouskidscanada@theconversation.com">CuriousKidsCanada@theconversation.com</a>.</em></p>
<blockquote>
<p><strong>Why are the northern lights only spotted at areas around the poles? — Naba, 9, Oakville, Ont.</strong></p>
</blockquote>
<p>The northern lights are also called auroras, and they are regularly visible near Earth’s North and South Poles. They are a direct connection between the Earth and what’s happening on the sun.</p>
<p>Did you know that the sun has weather? But unlike Earth’s weather, the sun’s weather can affect the entire solar system! We call it space weather.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/solar-weather-has-real-material-effects-on-earth-118453">Solar weather has real, material effects on Earth</a>
</strong>
</em>
</p>
<hr>
<p>The sun is constantly blowing a spray of tiny particles in all directions, called the solar wind. This wind isn’t made of air, like on Earth. It’s made of mostly hydrogen, and it’s blowing at hundreds of kilometres per second (this is more than a thousand times faster than hurricane-force wind on Earth). </p>
<p>This incredibly fast wind has been blowing on to the Earth for billions of years, so why hasn’t it blown away Earth’s air by crashing into us?</p>
<p>Fortunately, for living things like us, the Earth has a magnetic field, which causes the planet to act like a giant magnet in space and protects Earth from the solar wind. Earth’s magnetic field is what causes <a href="https://www.livescience.com/32732-how-does-a-compass-work.html">a compass to work</a>. <a href="https://www.steampoweredfamily.com/activities/how-to-make-a-compass/">The small magnet in a compass</a> aligns with Earth’s magnetic field and always points to Earth’s magnetic North Pole. Earth’s magnetic field is totally invisible to our eyes, but we can <a href="https://www.geomag.nrcan.gc.ca/mag_fld/default-en.php">measure it with magnets and other scientific instruments</a>.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/o4FSg-90XlA?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">A NASA video showing how the Earth’s magnetic field protects from the solar wind.</span></figcaption>
</figure>
<p>The particles that make up the solar wind are deflected by Earth’s magnetic field, so they mostly pass around the Earth without crashing into us. But it’s not a perfect shield: because of the <a href="https://science.nasa.gov/science-news/news-articles/earths-magnetosphere">shape of Earth’s magnetic field</a>, close to the North and South Poles, a little bit of the solar wind can sometimes get through and crash directly into the Earth’s atmosphere.</p>
<p>This crash happens between very tiny particles at speeds much faster than a bullet, so the result is very different from than say, a car crash. Instead of throwing off smaller pieces or exploding, they emit light. The colours tell us about what type of atmospheric particle is being crashed into by the solar wind. Red and green are from oxygen collisions, and blue is from nitrogen.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/427892/original/file-20211021-24-1b9lal4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="the northern lights" src="https://images.theconversation.com/files/427892/original/file-20211021-24-1b9lal4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/427892/original/file-20211021-24-1b9lal4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=397&fit=crop&dpr=1 600w, https://images.theconversation.com/files/427892/original/file-20211021-24-1b9lal4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=397&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/427892/original/file-20211021-24-1b9lal4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=397&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/427892/original/file-20211021-24-1b9lal4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=499&fit=crop&dpr=1 754w, https://images.theconversation.com/files/427892/original/file-20211021-24-1b9lal4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=499&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/427892/original/file-20211021-24-1b9lal4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=499&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The northern lights as seen from Iceland.</span>
<span class="attribution"><span class="source">(Shutterstock)</span></span>
</figcaption>
</figure>
<h2>Space weather</h2>
<p>Exactly what the auroras look like depends a bit on the state of Earth’s magnetic field and atmosphere, but more directly depends on space weather. Sometimes the sun produces a storm, called a <a href="https://www.swpc.noaa.gov/phenomena/solar-flares-radio-blackouts">solar flare</a> or a <a href="https://earthsky.org/space/what-are-coronal-mass-ejections/">coronal mass ejection</a>, when there are suddenly a lot more particles injected into the solar wind, making it stronger than usual. Because we have telescopes <a href="https://sohowww.nascom.nasa.gov/">in space</a> and <a href="http://obs.astro.ucla.edu/intro.html">on Earth</a> that carefully watch the sun for these storms, we usually have two to three days warning before a storm hits the Earth.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/space-weather-is-difficult-to-predict-with-only-an-hour-to-prevent-disasters-on-earth-159895">Space weather is difficult to predict — with only an hour to prevent disasters on Earth</a>
</strong>
</em>
</p>
<hr>
<p>Typically, a solar storm will cause an impressive display of auroras only for people who live in the far north and south of the world, underneath the part of Earth’s magnetic field that can let the solar wind through. But sometimes, a really powerful storm can cause the auroras to be visible much closer to the equator. </p>
<p>When this happens, it means that a lot of the solar wind particles are crashing all over Earth’s atmosphere. It’s not dangerous to us directly because we’re protected from these fast-moving particles by Earth’s atmosphere. But astronauts who are above the atmosphere may have <a href="https://www.space.com/3247-astronauts-sleep-safety-solar-flare.html">to take shelter in a heavily shielded part of the space station</a>, and satellites can be temporarily shut down or even broken.</p>
<p>On very rare occasions, the auroras caused by a solar storm can be so powerful that <a href="https://www.nasa.gov/topics/earth/features/sun_darkness.html">electrical lines</a> on Earth can be damaged, causing many people to <a href="https://www.washingtonpost.com/news/capital-weather-gang/wp/2013/10/31/the-scary-halloween-solar-storm-of-2003-a-warning-for-todays-space-weather/">lose power</a>.</p>
<p>The sun has a cycle of storms: <a href="https://spaceplace.nasa.gov/solar-cycles/">it has more frequent storms every 11 years</a>, which is called the solar maximum. When the sun is near solar maximum, auroras are more likely to happen. The next solar maximum is <a href="https://www.nasa.gov/press-release/solar-cycle-25-is-here-nasa-noaa-scientists-explain-what-that-means">predicted to be in late 2024 or early 2025</a>, so we will have more and more auroras to watch over the next few years.</p>
<p>If you want to see auroras, you can check the <a href="https://spaceweather.com/">space weather forecast</a> every night just like you can check your local weather forecast every day.</p>
<p>In places close to the poles, where people have been watching auroras for as long as we’ve been human, <a href="https://newsinteractives.cbc.ca/longform/legends-of-the-northern-lights">many cultures understand the lights as a cosmic connection</a>. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/fire-in-the-sky-the-southern-lights-in-indigenous-oral-traditions-39113">Fire in the sky: The southern lights in Indigenous oral traditions</a>
</strong>
</em>
</p>
<hr>
<p>A truly bright auroral display is an incredible experience. It’s a powerful reminder of connection between the Earth’s atmosphere, magnetic field and the sun, all of which are vitally important to life on Earth. </p>
<hr>
<p><em>Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to <a href="mailto:curiouskidscanada@theconversation.com">CuriousKidsCanada@theconversation.com</a>. Please tell us your name, age and the city where you live.</em>
<em>And since curiosity has no age limit — adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.</em></p>
<hr><img src="https://counter.theconversation.com/content/165000/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Samantha Lawler receives funding from the Natural Sciences and Engineering Research Council of Canada.</span></em></p>A curious kid asks: Why are the northern lights only spotted at areas around the poles?Samantha Lawler, Assistant professor of astronomy, University of ReginaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1680322021-09-16T14:17:54Z2021-09-16T14:17:54ZDo the northern lights make sounds that you can hear?<figure><img src="https://images.theconversation.com/files/421574/original/file-20210916-13-39kdxt.jpeg?ixlib=rb-1.1.0&rect=14%2C0%2C4977%2C3173&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/spectacular-auroral-display-over-glacier-lagoon-143438332">John A Davis/Shutterstock</a></span></figcaption></figure><p>It’s a question that has <a href="https://royalsocietypublishing.org/doi/full/10.1098/rsnr.2021.0031">puzzled observers for centuries</a>: do the fantastic green and crimson light displays of the aurora borealis produce any discernible sound? </p>
<p>Conjured by the interaction of solar particles with gas molecules in Earth’s atmosphere, the aurora generally occurs <a href="https://www.ncei.noaa.gov/news/science-beauty-and-mystery-auroras">near Earth’s poles</a>, where the magnetic field is strongest. Reports of the aurora making a noise, however, are rare – and were historically dismissed by scientists.</p>
<p>But a <a href="https://www.researchgate.net/profile/Unto-Laine/publication/304252270_Auroral_Acoustics_project_-_a_progress_report_with_a_new_hypothesis/links/576aba0208aefcf135bd4c60/Auroral-Acoustics-project-a-progress-report-with-a-new-hypothesis.pdf">Finnish study</a> in 2016 claimed to have finally confirmed that the northern lights really do produce sound audible to the human ear. <a href="https://www.youtube.com/watch?v=NRZfKqhs6rM&ab_channel=AaltoUniversity">A recording</a> made by one of the researchers involved in the study even claimed to have captured the sound made by the captivating lights 70 metres above ground level.</p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/NRZfKqhs6rM?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p>Still, the mechanism behind the sound remains somewhat mysterious, as are the conditions that must be met for the sound to be heard. <a href="https://royalsocietypublishing.org/doi/full/10.1098/rsnr.2021.0031">My recent research</a> takes a look over historic reports of auroral sound to understand the methods of investigating this elusive phenomenon and the process of establishing whether reported sounds were objective, illusory of imaginary.</p>
<h2>Historic claims</h2>
<p>Auroral noise was the subject of particularly lively debate in the first decades of the 20th century, when accounts from settlements across northern latitudes reported that sound sometimes accompanied the mesmerising light displays in their skies.</p>
<p>Witnesses told of a quiet, almost imperceptible crackling, whooshing or whizzing noise during particularly violent northern lights displays. In the early 1930s, for instance, <a href="https://royalsocietypublishing.org/doi/full/10.1098/rsnr.2021.0031">personal testimonies</a> started flooding into The Shetland News, the weekly newspaper of the subarctic Shetland Islands, likening the sound of the northern lights to “rustling silk” or “two planks meeting flat ways”.</p>
<p>These tales were corroborated by similar testimony from northern Canada and Norway. Yet the scientific community was less than convinced, especially considering very few western explorers claimed to have heard the elusive noises themselves.</p>
<figure class="align-center ">
<img alt="A black and white image of aurora" src="https://images.theconversation.com/files/421594/original/file-20210916-15-7ooisf.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/421594/original/file-20210916-15-7ooisf.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=528&fit=crop&dpr=1 600w, https://images.theconversation.com/files/421594/original/file-20210916-15-7ooisf.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=528&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/421594/original/file-20210916-15-7ooisf.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=528&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/421594/original/file-20210916-15-7ooisf.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=664&fit=crop&dpr=1 754w, https://images.theconversation.com/files/421594/original/file-20210916-15-7ooisf.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=664&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/421594/original/file-20210916-15-7ooisf.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=664&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">An early photograph of the aurora, captured in 1930 in Finnmark, Norway.</span>
<span class="attribution"><span class="source">Nasjonalbiblioteket, Norway</span></span>
</figcaption>
</figure>
<p>The credibility of auroral noise reports from this time was intimately tied to altitude measurements of the northern lights. It was considered that only those displays that descended low into the Earth’s atmosphere would be able to transmit sound which could be heard by the human ear. </p>
<p>The problem here was that results recorded during the <a href="https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/TR015i001p00166-2">Second International Polar Year of 1932-3</a> found aurorae most commonly took place 100km above Earth, and very rarely below 80km. This suggested it would be impossible for discernible sound from the lights to be transmitted to the Earth’s surface.</p>
<h2>Auditory illusions?</h2>
<p>Given these findings, eminent physicists and meteorologists remained sceptical, dismissing accounts of auroral sound and very low aurorae as folkloric stories or auditory illusions. </p>
<p>Sir Oliver Lodge, the British physicist involved in the development of radio technology, <a href="https://royalsocietypublishing.org/doi/full/10.1098/rsnr.2021.0031">commented that</a> auroral sound might be a psychological phenomenon due to the vividness of the aurora’s appearance – just as meteors sometimes <a href="https://www.nature.com/articles/023529e0">conjure a whooshing sound</a> in the brain. Similarly, the meteorologist George Clark Simpson argued that the appearance of low aurorae was likely an <a href="https://www.nature.com/articles/127663a0">optical illusion</a> caused by the interference of low clouds.</p>
<p>Nevertheless, the leading auroral scientist of the 20th century, Carl Størmer, <a href="https://www.nature.com/articles/119045b0">published accounts</a> written by two of his assistants who claimed to have heard the aurora, adding some legitimacy to the large volume of personal reports. </p>
<figure class="align-center ">
<img alt="A scientist in the snow" src="https://images.theconversation.com/files/421583/original/file-20210916-23-1tkr9v2.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/421583/original/file-20210916-23-1tkr9v2.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=500&fit=crop&dpr=1 600w, https://images.theconversation.com/files/421583/original/file-20210916-23-1tkr9v2.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=500&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/421583/original/file-20210916-23-1tkr9v2.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=500&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/421583/original/file-20210916-23-1tkr9v2.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=629&fit=crop&dpr=1 754w, https://images.theconversation.com/files/421583/original/file-20210916-23-1tkr9v2.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=629&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/421583/original/file-20210916-23-1tkr9v2.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=629&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Carl Størmer observing the northern lights.</span>
<span class="attribution"><a class="source" href="https://www.nb.no/items/eddfe10bb9dd8e017ad15ae8b305bbf4?page=0&searchText=carl%20stormer">Nasjonalbiblioteket, Norway</a></span>
</figcaption>
</figure>
<p>Størmer’s assistant Hans Jelstrup said he had heard a “very curious faint whistling sound, distinctly undulatory, which seemed to follow exactly the vibrations of the aurora”, while Mr Tjönn experienced a sound like “burning grass or spray”. As convincing as these two last testimonies may have been, they still didn’t propose a mechanism by which auroral sound could operate.</p>
<h2>Sound and light</h2>
<p>The answer to this enduring mystery which has subsequently garnered the most support was first tentatively suggested in 1923 by <a href="http://adsabs.harvard.edu/pdf/1923JRASC..17..273C">Clarence Chant</a>, a well-known Canadian astronomer. He argued that the motion of the northern lights alters Earth’s magnetic field, inducing changes in the electrification of the atmosphere, even at a significant distance. </p>
<p>This electrification produces a crackling sound much closer to Earth’s surface when it meets objects on the ground, much like the sound of static. This could take place on the observer’s clothes or spectacles, or possibly in surrounding objects including fir trees or the cladding of buildings. </p>
<p>Chant’s theory correlates well with many accounts of auroral sound, and is also supported by occasional reports of the smell of ozone – which reportedly carries a <a href="https://www.scientificamerican.com/article/storm-scents-smell-rain/">metallic odour</a> similar to an electrical spark – during northern lights displays. </p>
<p>Yet Chant’s paper went largely unnoticed in the 1920s, only receiving recognition in the 1970s when <a href="https://www.sciencedirect.com/science/article/pii/S0065268708603520?casa_token=A_jSDHN45qoAAAAA:2Cb-cn5RsGRYmBvvOAdcMO5jY5PL5KLK1vvhn_xB-iCzdABUFIUG9CtpPcoR2ho-lVtLdxM1m-o">two auroral physicists</a> revisited the historical evidence. Chant’s theory is largely accepted by scientists today, although there’s <a href="https://research.aalto.fi/en/publications/localization-of-sound-sources-in-temperature-inversion-layer-duri/fingerprints/?sortBy=alphabetically">still debate</a> as to how exactly the mechanism for producing the sound operates. </p>
<p>What is clear is that the aurora does, on rare occasions, make sounds audible to the human ear. The eerie reports of crackling, whizzing and buzzing noises accompanying the lights describe an objective audible experience – not something illusory or imagined.</p>
<h2>Sampling the sound</h2>
<p>If you want to hear the northern lights for yourself, you may have to spend a considerable amount of time in the Polar regions, considering the aural phenomenon only presents itself in <a href="http://adsabs.harvard.edu/pdf/1933JRASC..27..184B">5% of violent auroral displays</a>. It’s also most commonly heard on the top of mountains, surrounded by only a few buildings – so it’s not an especially accessible experience. </p>
<p>In recent years, the sound of the aurora has nonetheless been explored for its aesthetic value, inspiring musical compositions and laying the foundation for novel ways of interacting with its electromagnetic signals. </p>
<p>The Latvian composer <a href="https://d1wqtxts1xzle7.cloudfront.net/60412911/DUE_NORTH__ERIKS_ESENVALDS_AND_AURORA_BOREALIS_AS_A_CLAIMED_ARTISTIC_SPACE-with-cover-page-v2.pdf?Expires=1631459602&Signature=B-TmBsJ4tS5TRtn4FXi-qnTLs64dLuUR9EqiE7Jcqv9vPUf8FQqvjDAp9eeMyNg-guwTUOVVYxskN41O6jUyRCzdq1Z1NnusC%7E%7EWt5RNzxEdFsh7iEs%7EexnZvm14xwn-SmBp6gi30tVW3wxoV1qqL0Rprl4ZMWmmAUtGU8g6YB%7EpBxq9udl-XEfAOyOoOonKRkFZYpg8ybvAia7bZu9vaAlBYLP7ZJu0jvTjN4sA830Mz9051KuFcArUVccA51pmdc4Y72%7ExdbwxhBft7g6frPVO1QlfbS2OMgWisCdcx4dUtP0IVWvI6Dv9PceF86EW6x7CmSsnkUnsSuJuKYzxVA__&Key-Pair-Id=APKAJLOHF5GGSLRBV4ZA">Ēriks Ešenvalds</a> has used journal extracts from the American explorer Charles Hall and the Norwegian statesman Fridjtof Nansen, both of whom claimed to have heard the northern lights, in his music. His composition, <a href="https://www.youtube.com/watch?v=jh09QDoJMMg">Northern Lights</a>, interweaves these reports with the only known Latvian folksong recounting the auroral sound phenomenon, sung by a tenor solo.</p>
<p>Or you can also listen to the radio signals of the northern lights at home. In 2020, a <a href="https://www.bbc.co.uk/programmes/m000qhj3">BBC 3 radio programme</a> remapped very low frequency radio recordings of the aurora onto the audible spectrum. Although not the same as perceiving audible noises produced by the the northern lights in person on a snowy mountaintop, these radio frequencies give an awesome sense of the aurora’s transitory, fleeting and dynamic nature.</p><img src="https://counter.theconversation.com/content/168032/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Fiona Amery does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Depending on who you ask, the northern lights may, very occasionally, sound like ‘rustling silk’ or ‘two planks meeting flat ways’.Fiona Amery, PhD Candidate in History and Philosophy of Science, University of CambridgeLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1554452021-03-23T02:53:31Z2021-03-23T02:53:31ZClimate explained: how particles ejected from the Sun affect Earth’s climate<figure><img src="https://images.theconversation.com/files/386315/original/file-20210224-17-sbtks2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Earth's magnetic field protects us from the solar wind, guiding the solar particles to the polar regions.</span> <span class="attribution"><a class="source" href="https://sohowww.nascom.nasa.gov/gallery/images/sunearth01.html">SOHO (ESA & NASA)</a></span></figcaption></figure><figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
<span class="attribution"><a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p><em><strong><a href="https://theconversation.com/nz/topics/climate-explained-74664">Climate Explained</a></strong> is a collaboration between The Conversation, Stuff and the New Zealand Science Media Centre to answer your questions about climate change.</em> </p>
<p><em>If you have a question you’d like an expert to answer, please send it to <a href="mailto:climate.change@stuff.co.nz">climate.change@stuff.co.nz</a></em></p>
<hr>
<blockquote>
<p><strong>When the Sun ejects solar particles into space, how does this affect the Earth and climate? Are clouds affected by these particles?</strong></p>
</blockquote>
<p>When we consider the Sun’s influence on Earth and our climate, we tend to think about solar radiation. We are acutely aware of the skin-burning dangers of ultraviolet, or UV, radiation. </p>
<p>But the Sun is an active star. It also continuously releases what is known as “<a href="https://en.wikipedia.org/wiki/Solar_wind">solar wind</a>”, made up of charged particles, largely protons and electrons, that travel at speeds of hundreds of kilometres per hour.</p>
<p>Some of these particles that reach Earth are guided into the polar atmosphere by our magnetic field. As a result, we can see the southern lights, aurora australis, in the southern hemisphere, and the northern equivalent, aurora borealis. </p>
<figure class="align-center ">
<img alt="Aurora Australis" src="https://images.theconversation.com/files/389700/original/file-20210315-21-hbzclj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/389700/original/file-20210315-21-hbzclj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=372&fit=crop&dpr=1 600w, https://images.theconversation.com/files/389700/original/file-20210315-21-hbzclj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=372&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/389700/original/file-20210315-21-hbzclj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=372&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/389700/original/file-20210315-21-hbzclj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=467&fit=crop&dpr=1 754w, https://images.theconversation.com/files/389700/original/file-20210315-21-hbzclj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=467&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/389700/original/file-20210315-21-hbzclj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=467&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Aurora australis observed above southern New Zealand.</span>
<span class="attribution"><span class="source">Shutterstock/Fotos593</span></span>
</figcaption>
</figure>
<p>This visible manifestation of solar particles entering Earth’s atmosphere is a constant reminder there is more to the Sun than sunlight. But the particles have other effects as well. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/why-is-the-suns-atmosphere-so-hot-spacecraft-starts-to-unravel-our-stars-mysteries-128242">Why is the sun's atmosphere so hot? Spacecraft starts to unravel our star's mysteries</a>
</strong>
</em>
</p>
<hr>
<h2>Solar particles and ozone</h2>
<p>When solar particles enter the atmosphere, their high energies ionise neutral atmospheric nitrogen and oxygen molecules, which make up 99% of the atmosphere. This “<a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2016GL068279">energetic particle precipitation</a>”, named because it’s like a rain of particles from space, is a major source of <a href="https://progearthplanetsci.springeropen.com/articles/10.1186/s40645-014-0024-3">ionisation in the polar atmosphere</a> above 30km altitude — and it sets off a chain of reactions that produces <a href="https://aura.gsfc.nasa.gov/science/feature-20200701.html">chemicals</a> that facilitate the <a href="https://www.nobelprize.org/prizes/chemistry/1995/crutzen/lecture/">destruction of ozone</a>. </p>
<p>The impact of solar particles on atmospheric ozone was first observed in 1969. Since the early 2000s, thanks to new kinds of satellite observations, we have seen growing evidence that solar particles play an <a href="https://www.nature.com/articles/ncomms6197">important part</a> in influencing polar ozone. During particularly active times, when the Sun releases large amounts of particles into space, up to 60% of ozone at altitudes above 50km can be depleted. The effect can last for weeks.</p>
<p>Lower down in the atmosphere, below 50km, solar particles are important contributors to the year-to-year variability in polar ozone levels, often through <a href="https://progearthplanetsci.springeropen.com/articles/10.1186/s40645-014-0024-3">indirect pathways</a>. Here, solar particles again contribute to <a href="https://ozonewatch.gsfc.nasa.gov/facts/">ozone loss</a>, but a recent discovery showed they also help curb some of the <a href="https://doi.org/10.5194/acp-21-2819-2021">depletion in the Antarctic ozone hole</a>.</p>
<h2>How ozone affects the climate</h2>
<p>Most of the ozone in the atmosphere resides in a thin layer at altitudes of 20-25km — the “<a href="https://scied.ucar.edu/learning-zone/atmosphere/ozone-layer">ozone layer</a>”. </p>
<p>But ozone is everywhere in the atmosphere, from the Earth’s surface to altitudes above 100km. It is a greenhouse gas and plays a key role in heating and cooling the atmosphere, which makes it critical for climate. </p>
<p>In the southern hemisphere, <a href="https://doi.org/10.1002/qj.2330">changes in polar ozone</a> are known to influence regional climate conditions. </p>
<figure class="align-center ">
<img alt="Satellite image of Earth's atmosphere" src="https://images.theconversation.com/files/389699/original/file-20210315-17-gr8nv2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/389699/original/file-20210315-17-gr8nv2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=364&fit=crop&dpr=1 600w, https://images.theconversation.com/files/389699/original/file-20210315-17-gr8nv2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=364&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/389699/original/file-20210315-17-gr8nv2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=364&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/389699/original/file-20210315-17-gr8nv2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=457&fit=crop&dpr=1 754w, https://images.theconversation.com/files/389699/original/file-20210315-17-gr8nv2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=457&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/389699/original/file-20210315-17-gr8nv2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=457&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Solar particles ionise nitrogen and oxygen molecules in the atmosphere, which leads to other chemical reactions that contribute to ozone destruction.</span>
<span class="attribution"><span class="source">Shutterstock/PunyaFamily</span></span>
</figcaption>
</figure>
<p>Its depletion above Antarctica had a cooling effect, which in turn pulled the westerly wind jet that circles the continent closer. As the Antarctic hole recovers, this <a href="https://www.uow.edu.au/media/2019/ozone-depletion-driving-climate-change-in-southern-hemisphere.php">wind belt can meander further north</a> and affect rainfall patterns, sea-surface temperatures and ocean currents. The <a href="https://niwa.co.nz/climate/information-and-resources/southern-annular-mode">Southern Annular Mode</a> describes this north-south movement of the wind belt that circles the southern polar region.</p>
<p>Ozone is important for future climate predictions, not only in the thin ozone layer, but throughout the atmosphere. It is crucial we understand the factors that influence ozone variability, be it man-made or natural like the Sun. </p>
<h2>The Sun’s direct influence</h2>
<p>The link between solar particles and ozone is reasonably well established, but what about any direct effects solar particles may have on the climate? </p>
<p>We have observational evidence that solar activity influences <a href="https://doi.org/10.1029/2008JA014029">regional climate variability at both poles</a>. Climate models also suggest such polar effects link to larger climate patterns (such as the Northern and Southern Annular Modes) and influence conditions in mid-latitudes. </p>
<p>The details are not yet well understood, but for the first time the influence of <a href="https://doi.org/10.5194/gmd-10-2247-2017">solar particles on the climate system</a> will be included in climate simulations used for the upcoming Intergovernmental Panel on Climate Change (<a href="https://www.ipcc.ch/">IPCC</a>) assessment.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/solar-weather-has-real-material-effects-on-earth-118453">Solar weather has real, material effects on Earth</a>
</strong>
</em>
</p>
<hr>
<p>Through solar radiation and particles, the Sun provides a key energy input to our climate system. While these do vary with the Sun’s 11-year cycle of magnetic activity, they can not explain the recent rapid increase in global temperatures due to climate change.</p>
<p>We know rising levels of <a href="https://www.acs.org/content/acs/en/climatescience/greenhousegases.html">greenhouse gases</a> in the atmosphere are pushing up Earth’s surface temperature (the physics have been known <a href="https://www.sciencedirect.com/science/article/pii/S0160932716300308">since the 1800s</a>). We also know human activities have greatly <a href="https://www.esrl.noaa.gov/gmd/ccgg/trends/">increased greenhouse gases</a> in the atmosphere. Together these two factors explain the observed rise in global temperatures.</p>
<h2>What about clouds?</h2>
<p>Clouds are much lower in the atmosphere than where most solar particles penetrate. Particles know as galactic cosmic rays (coming from the centre of our galaxy rather than the Sun) may be linked to cloud formation. </p>
<p>It has been suggested cosmic rays could influence the formation of condensation nuclei, which act as “seeds” for clouds. But recent <a href="https://doi.org/10.1002/2017JD027475">research</a> at the <a href="https://home.cern/">CERN</a> nuclear research facility suggests the effects are insignificant. </p>
<p>This doesn’t rule out some other mechanisms for cosmic rays to affect cloud formation, but thus far there is little supporting evidence.</p><img src="https://counter.theconversation.com/content/155445/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Annika Seppälä is a Senior Lecturer at the University of Otago. She has previously received research funding from the European Council and the Academy of Finland.</span></em></p>When solar particles reach the Earth, they not only produce spectacular auroras but also contribute to the chemical reactions leading to ozone depletion, which in turn influences climate patterns.Annika Seppälä, Senior Lecturer in Geophysics, University of OtagoLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1115732019-02-12T12:33:10Z2019-02-12T12:33:10ZCurious Kids: what causes the northern lights?<figure><img src="https://images.theconversation.com/files/258503/original/file-20190212-174887-2wfoul.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C4851%2C3224&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A magical sight. </span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/ronel_reyes/8479833336/sizes/l">Ronel Reyes/Flickr.</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span></figcaption></figure><p><em><a href="https://theconversation.com/au/topics/curious-kids-36782">Curious Kids</a> is a series by <a href="https://theconversation.com/uk">The Conversation</a>, which gives children of all ages the chance to have their questions about the world answered by experts. All questions are welcome: find out how to enter at the bottom of this article.</em> </p>
<hr>
<blockquote>
<p><strong>What causes the northern lights? – Ffion, age 6.75, Pembrokeshire, UK.</strong></p>
</blockquote>
<p>I first saw the <a href="https://theconversation.com/uk/topics/northern-lights-14791">northern lights</a> three years ago, while driving home one night. They were so beautiful, I had to stop the car and get out to have a proper look, even though it was cold. Although the northern lights might look like magic, they can actually be explained by science – with a bit of help from the Sun, birds and fizzy drinks. </p>
<p>The energy for making the northern lights comes from the Sun. The Sun creates something called the “solar wind”. This is different to the light that we get from the Sun, which keeps us warm and helps us to see during the day.</p>
<p>This solar wind drifts away from the Sun through space, carrying tiny particles called protons and electrons. Protons and electrons are some of the tiny building blocks that make up most of the stuff in the universe, like plants and chocolate and me and you.</p>
<p>Think of the smallest Lego bricks you have in your toy box, which can be stuck together to make bigger things - these are what protons and electrons (and neutrons too) are to the universe. These particles carry lots of energy from the Sun, on their journey through space.</p>
<h2>The solar wind</h2>
<p>Sometimes the solar wind is strong, and sometimes it’s weak. We can only see the northern lights at times when the solar wind is strong enough. </p>
<p>When the solar wind reaches planet Earth, something very interesting happens: it runs into the Earth’s magnetic field. The magnetic field forces the solar wind away, and makes it travel around the Earth instead.</p>
<p>The magnetic field is what makes the needle on a compass point north, and is how birds know where to go when they migrate – it’s also why we have the north and south poles at all. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/fVsONlc3OUY?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p>The magnetic field interacts with the solar wind and guides the protons and electrons down towards Earth along the magnetic field, away from the middle of the planet and toward the north and south poles.</p>
<p>Because of this, we get both northern and <a href="https://theconversation.com/uk/topics/southern-lights-15736">southern lights</a> – also known as the <a href="https://theconversation.com/uk/topics/aurora-borealis-14790">aurora borealis</a> and the <a href="https://theconversation.com/uk/topics/aurora-australis-15735">aurora australis</a>. </p>
<h2>Shake it up</h2>
<p>When the solar wind gets past the magnetic field and travels towards the Earth, it runs into the atmosphere. The atmosphere is like a big blanket of gas surrounding our planet, which contains lots of different particles that make up the air that we breathe and help to protect us from harmful radiation from the Sun. </p>
<p>As the protons and electrons from the solar wind hit the particles in the Earth’s atmosphere, they release energy – and this is what causes the northern lights. </p>
<p>Here’s how it happens: imagine you have a bottle of fizzy drink, and you give it a good shake. This puts lots of energy into the bottle, and when you open it, this energy will be released in a big stream of fizzy bubbles. </p>
<p>In the same way, the protons and electrons from the Sun “shake up” the particles in the atmosphere. Then, the particles let out all that energy in the form of light (instead of bubbles). </p>
<p>Different types of particles in the atmosphere make different colours after they’re shaken up – oxygen makes red and green light, and nitrogen makes blue light. Our eyes see green best out of all the colours, so we see green the brightest when we look at the northern lights.</p>
<p>It is easiest to see the northern lights in winter when is it very dark at night, and also outside of cities and away from street lights. You are more likely to see them the further north you are too. Check out this great website <a href="https://aurorawatch.lancs.ac.uk/">Aurora Watch</a> from Lancaster University – it might just help you find them!</p>
<p><em>This article has been corrected: the Earth’s magnetic field is not weaker at the poles, as the article originally stated.</em></p>
<hr>
<figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=376&fit=crop&dpr=1 600w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=376&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=376&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=472&fit=crop&dpr=1 754w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=472&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=472&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
<span class="attribution"><a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
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</figure>
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<p><em>More <a href="https://theconversation.com/topics/curious-kids-36782?utm_source=TCUK&utm_medium=linkback&utm_campaign=TCUKengagement&utm_content=CuriousKidsUK">Curious Kids</a> articles, written by academic experts:</em></p>
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<li><p><em><a href="https://theconversation.com/curious-kids-why-do-spiders-have-hairy-legs-108602?utm_source=TCUK&utm_medium=linkback&utm_campaign=TCUKengagement&utm_content=CuriousKidsUK">Why do spiders have hairy legs? - Audrey, age five, Melbourne, Australia</a></em></p></li>
<li><p><em><a href="https://theconversation.com/curious-kids-why-are-there-different-seasons-at-specific-times-of-the-year-109380?utm_source=TCUK&utm_medium=linkback&utm_campaign=TCUKengagement&utm_content=CuriousKidsUK">Why do we have different seasons at specific times of the year? – Shrey, age nine, Mumbai, India</a></em></p></li>
<li><p><em><a href="https://theconversation.com/curious-kids-how-is-water-made-109434?utm_source=TCUK&utm_medium=linkback&utm_campaign=TCUKengagement&utm_content=CuriousKidsUK">How is water made? – Clara, age eight, Canberra, Australia</a></em></p></li>
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<p class="fine-print"><em><span>Paul O'Mahoney does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>The northern lights might look like magic, but they can actually be explained by science – here’s how.Paul O'Mahoney, Post-Doctoral Research Assistant in Photobiology, University of DundeeLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/927112018-03-29T10:29:39Z2018-03-29T10:29:39ZSpace weather threatens high-tech life<figure><img src="https://images.theconversation.com/files/212007/original/file-20180326-159081-ibu4ks.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A coronal mass ejection erupts from the sun in 2012.</span> <span class="attribution"><a class="source" href="https://svs.gsfc.nasa.gov/11095">NASA</a></span></figcaption></figure><p>Shortly after 4 a.m. on a crisp, cloudless September morning in 1859, the sky above what is currently Colorado erupted in bright red and green colors. Fooled by the brightness into <a href="https://arstechnica.com/science/2012/05/1859s-great-auroral-stormthe-week-the-sun-touched-the-earth/">thinking it was an early dawn</a>, gold-rush miners in the mountainous region of what was then called the Kansas Territory woke up and started making breakfast. What happened in more developed regions was even more disorienting, and carries a warning for the wired high-tech world of the 21st century.</p>
<p>As the sky lit up over the nighttime side of the Earth, <a href="https://io9.gizmodo.com/how-the-carrington-event-let-telegraphs-run-on-aurora-p-1686759750">telegraph systems worldwide went berserk</a>, clacking nonsense code and emitting large sparks that ignited fires in nearby piles of paper tape. Telegraph operators <a href="https://science.nasa.gov/science-news/science-at-nasa/2008/06may_carringtonflare">suffered electrical burns</a>. Even disconnecting the telegraph units from their power sources <a href="https://science.nasa.gov/science-news/science-at-nasa/2008/06may_carringtonflare">didn’t stop the frenzy</a>, because the transmission wires themselves were carrying huge electrical currents. Modern technology had just been humbled by a fierce space weather storm that had arrived from the sun, the <a href="http://doi.org/10.1029/2011SW000734">largest ever recorded</a> – and more than twice as powerful as a storm nine years earlier, which had itself been the largest in known history.</p>
<p>My seven years of research on predicting solar storms, combined with my decades using GPS satellite signals under <a href="http://www.cis.rit.edu/%7Errdpci/space-weather.html">various solar storm conditions</a>, indicate that today’s even more sensitive electronics and satellites would be devastated should an event of that magnitude occur again. In 2008, a panel of experts commissioned by the National Academy of Sciences issued a detailed report with a sobering conclusion: The world would be <a href="https://www.nap.edu/catalog/12643/severe-space-weather-events-understanding-societal-and-economic-impacts-a">thrown back to the life of the early 1800s</a>, and it would take years – or even a decade – to recover from an event that large. </p>
<h2>A solar explosion</h2>
<p>Space weather storms have happened since the birth of the solar system, and have <a href="https://arxiv.org/ftp/arxiv/papers/0902/0902.3446.pdf">hit Earth many times</a>, both before and after that massive event in 1859, which was named the <a href="https://arstechnica.com/science/2012/05/1859s-great-auroral-stormthe-week-the-sun-touched-the-earth/">Carrington event</a> after a British astronomer who <a href="http://www.solarstorms.org/SCarrington.html">recorded his observations of the sun</a> at the time. They’re caused by huge electromagnetic explosions on the surface of the sun, called <a href="https://www.swpc.noaa.gov/phenomena/coronal-mass-ejections">coronal mass ejections</a>. Each explosion sends billions of protons and electrons, in a <a href="http://pluto.space.swri.edu/image/glossary/plasma.html">superheated ball of plasma</a>, out into the solar system.</p>
<p><a href="https://spacemath.gsfc.nasa.gov/weekly/3Page27.pdf">About 1 in every 20</a> coronal mass ejections heads in a direction that <a href="https://theconversation.com/how-facebook-the-wal-mart-of-the-internet-dismantled-online-subcultures-71536">intersects Earth’s orbit</a>. <a href="https://www.spaceweatherlive.com/en/help/how-do-we-know-if-a-cme-is-earth-directed-and-when-its-going-to-arrive">Around three days later</a>, our planet experiences what is called a space weather storm or a geomagnetic storm. </p>
<p>While these events are described using terms like “weather” and “storm,” they do not affect whether it’s rainy or sunny, hot or cold, or other aspects of what it’s like outdoors on any given day. Their effects are not meteorological, but only electromagnetic. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/212010/original/file-20180326-159081-14mbyu0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/212010/original/file-20180326-159081-14mbyu0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/212010/original/file-20180326-159081-14mbyu0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/212010/original/file-20180326-159081-14mbyu0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/212010/original/file-20180326-159081-14mbyu0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/212010/original/file-20180326-159081-14mbyu0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/212010/original/file-20180326-159081-14mbyu0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/212010/original/file-20180326-159081-14mbyu0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Aurorae are signs of a geomagnetic storm.</span>
<span class="attribution"><a class="source" href="https://www.nasa.gov/image-feature/goddard/2017/northern-lights-over-alaska-2">NASA/Terry Zaperach</a></span>
</figcaption>
</figure>
<h2>Hitting Earth</h2>
<p>When the coronal mass ejection arrives at Earth, the charged particles collide with air molecules in the upper atmosphere, generating heat and <a href="https://www.timeanddate.com/astronomy/northern-southern-lights.html">light called aurora</a>.</p>
<p>Also, as happens anytime <a href="https://www.youtube.com/watch?v=DVcvKwEUYqk">moving electrical charges encounter a magnetic field</a>, the interaction creates a spontaneous electrical current in any conductor that’s available. If the plasma ball is big enough, its interaction with Earth’s magnetic field can induce <a href="https://doi.org/10.1002/swe.20065">large currents on long wires</a> on the ground, like the one that overloaded telegraph circuits in 1859.</p>
<p><iframe id="6KR2O" class="tc-infographic-datawrapper" src="https://datawrapper.dwcdn.net/6KR2O/2/" height="400px" width="100%" style="border: none" frameborder="0"></iframe></p>
<p>On March 13, 1989, a storm only about <a href="https://www.swpc.noaa.gov/noaa-scales-explanation">one-fifth as strong</a> as the Carrington event hit Earth. It induced a large surge of current in the long power lines of the <a href="http://www.hydroquebec.com/learning/notions-de-base/tempete-mars-1989.html">Hydro-Quebec power grid</a>, causing physical damage to transmission equipment and leaving <a href="https://www.scientificamerican.com/article/geomagnetic-storm-march-13-1989-extreme-space-weather/">6 million people without power for nine hours</a>. Another storm-induced power surge <a href="https://spectrum.ieee.org/energy/the-smarter-grid/a-perfect-storm-of-planetary-proportions">destroyed a large transformer</a> at a New Jersey nuclear plant. Even though a spare transformer was nearby, it still took <a href="http://www.solarstorms.org/SWChapter1.html">six months to remove and replace</a> the melted unit. Some people worried that the bright auroral lights meant <a href="https://www.washingtonpost.com/news/capital-weather-gang/wp/2017/06/08/trumps-budget-eliminates-program-that-detects-infrastructure-crippling-solar-storms/">nuclear war had broken out</a>.</p>
<p>And in October 2003, a rapid series of solar storms affected Earth. Collectively called the Halloween solar storm, this series <a href="https://www.nasa.gov/topics/solarsystem/features/halloween_storms.html">caused surges</a> that <a href="https://www.directionsmag.com/article/1510">threatened the North American power grid</a>. Its <a href="https://www.space.com/23396-scary-halloween-solar-storm-2003-anniversary.html">effects on satellites</a> made GPS navigation erratic and interrupted communications connections during the peak of the storm.</p>
<p>Larger storms will have wider effects, cause more damage and take longer to recover from.</p>
<h2>Wide-reaching effects</h2>
<p>Geomagnetic storms attack the lifeblood of modern technology: electricity. A space weather storm typically lasts for two or three days, during which the entire planet is subjected to powerful electromagnetic forces. The <a href="https://www.nap.edu/catalog/12643/severe-space-weather-events-understanding-societal-and-economic-impacts-a">National Academy of Sciences study</a> concluded that an especially massive storm would damage and shut down power grids and communications networks worldwide.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/209611/original/file-20180308-30961-ghoyz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/209611/original/file-20180308-30961-ghoyz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/209611/original/file-20180308-30961-ghoyz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=397&fit=crop&dpr=1 600w, https://images.theconversation.com/files/209611/original/file-20180308-30961-ghoyz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=397&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/209611/original/file-20180308-30961-ghoyz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=397&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/209611/original/file-20180308-30961-ghoyz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=499&fit=crop&dpr=1 754w, https://images.theconversation.com/files/209611/original/file-20180308-30961-ghoyz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=499&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/209611/original/file-20180308-30961-ghoyz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=499&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Electricity, shown in the upper right, is integrated into every aspect of modern life.</span>
<span class="attribution"><a class="source" href="https://www.fcc.gov/help/public-safety-tech-topic-19-communications-interdependencies">Federal Communications Commission</a></span>
</figcaption>
</figure>
<p>After the storm passed, there would be no simple way to restore power. Manufacturing plants that build replacements for burned-out lines or power transformers would have no electricity themselves. Trucks needed to deliver raw materials and finished equipment wouldn’t be able to fuel up, either: Gas pumps run on electricity. And what pumps were running would soon dry up, because electricity also runs the machinery that extracts oil from the ground and refines it into usable fuel. </p>
<p>With transportation stalled, food wouldn’t get from farms to stores. Even systems that seem non-technological, like public water supplies, would shut down: Their pumps and purification systems need electricity. People in developed countries would find themselves with no running water, no sewage systems, no refrigerated food, and no way to get any food or other necessities transported from far away. People in places with more basic economies would also be without needed supplies from afar.</p>
<p>It could take <a href="https://www.nap.edu/catalog/12643/severe-space-weather-events-understanding-societal-and-economic-impacts-a">between four and 10 years</a> to repair all the damage. In the meantime, people would need to grow their own food, find and carry and purify water, and cook meals over fires.</p>
<p>Some systems would continue to operate, of course: bicycles, horse-drawn carriages and sailing ships. But another type of equipment that would keep working provides a clue to preventing this type of disaster: Electric cars would continue to work, but only in places where there were solar panels and wind turbines to recharge them.</p>
<h2>Preparing and protecting</h2>
<p>Geomagnetic storms would affect those small-scale installations far less than grid-scale systems. It’s a basic principle of electricity and magnetism that the longer a wire that’s exposed to a moving magnetic field, the <a href="https://doi.org/10.1016/S1364-6826(02)00126-8">larger the current that’s induced</a> in that wire.</p>
<p>In 1859, the telegraph system was so profoundly affected because it had wires stretching from city to city across the U.S. Those very long wires had to handle enormous amounts of energy all at once, and failed. Today, there are long runs of wires connecting power generators to consumers – such as <a href="https://www.eia.gov/todayinenergy/detail.php?id=27152">from Niagara Falls to New York City</a> – that would be similarly susceptible to large induced currents.</p>
<p>The only way to reduce vulnerability to geomagnetic storms is to substantially revamp the power grid. Now, it is a <a href="https://www.eia.gov/todayinenergy/detail.php?id=27152">vast web of wires</a> that effectively spans continents. Governments, businesses and communities need to work together to split it into much smaller components, each serving a town or perhaps even a neighborhood – or an individual house. These “<a href="https://www.energy.gov/articles/how-microgrids-work">microgrids</a>” can be connected to each other, but should have <a href="https://science.nasa.gov/science-news/science-at-nasa/2010/26oct_solarshield">protections built in</a> to allow them to be disconnected quickly when a storm approaches. That way, the length of wires affected by the storm will be shorter, reducing the potential for damage.</p>
<p>A family using solar panels and batteries for storage and an electric car to get around would likely find its water supply, natural gas or internet service disrupted. But their freedom to travel, and to use electric lights to work after dark, would provide a much better chance at survival.</p>
<h2>When will the next storm hit?</h2>
<p>People should start preparing today. It’s impossible to know when a major storm will hit next: The most we’ll get is a <a href="https://theconversation.com/new-solar-storm-forecasting-technique-breaks-the-24-hour-warning-barrier-for-earth-42917">three-day warning</a> when something happens on the surface of the sun. It’s really only a matter of time before there is another one like the Carrington event.</p>
<p><a href="https://doi.org/10.1063/1.4993929">Solar astrophysicists</a> are also studying the sun to identify any events or conditions that might herald a coronal mass ejection. They’re collecting enormous amounts of data about the sun and using computer analysis to try to connect that information to geomagnetic storms on Earth. This work is underway and will become more refined over time. The research has not yet yielded a reliable prediction of a coming solar storm before an ejection occurs, but it improves each year. </p>
<p>In my view, the safest course of action involves developing microgrids based on renewable energy. That would not only improve people’s quality of life around the planet right now, but also provide the best opportunity to maintain that lifestyle when adverse events happen.</p><img src="https://counter.theconversation.com/content/92711/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Roger Dube has previously received funding from the National Aeronautics and Space Administration (NASA). </span></em></p>The wired Earth of the 21st century is at the mercy of the volatile nature of the sun.Roger Dube, Research Professor of Imaging Science, Rochester Institute of TechnologyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/836772017-09-08T00:18:31Z2017-09-08T00:18:31ZMassive sunspots and huge solar flares mean unexpected space weather for Earth<figure><img src="https://images.theconversation.com/files/185178/original/file-20170907-9585-c1fei2.jpg?ixlib=rb-1.1.0&rect=183%2C0%2C1615%2C1074&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A huge solar flare flashes in the middle of the sun on Sept. 6, 2017. A separate image of the Earth provides scale.</span> <span class="attribution"><a class="source" href="https://svs.gsfc.nasa.gov/12706">NASA/GSFC/SDO</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>If you still have your solar viewing glasses from the eclipse, now is a good time to slap them on and look up at the sun. You’ll see two big dark areas visible on our star. These massive sunspots are regions of intense and complicated magnetic fields that can produce solar flares – bursts of high-energy radiation. You can just make them out with solar viewing glasses, but they’re better viewed through a solar telescope. </p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"905107565406818304"}"></div></p>
<p>These two huge sunspots are currently causing quite a bit of consternation and interest. The solar storms they’ve sent toward Earth may affect communications and other technologies like GPS and radio signals. They’re causing amazing displays of the Northern and Southern Lights. And space weather scientists like us are excited because we wouldn’t normally expect this much activity from the sun at the moment.</p>
<p>The sun goes through 11-year cycles of solar activity. What scientists call a solar maximum is the time in the cycle when the sun is putting out the most energy. That’s when we tend to see the most sunspots, solar flares and associated solar storms. Some solar maxima are larger or more active than others – such as the 1990-1991 solar max. But this last cycle, which peaked in 2014, was <a href="https://solarscience.msfc.nasa.gov/predict.shtml">quite small</a>, and there were few large geomagnetic storms.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/185117/original/file-20170907-9538-1uarzku.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/185117/original/file-20170907-9538-1uarzku.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/185117/original/file-20170907-9538-1uarzku.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/185117/original/file-20170907-9538-1uarzku.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/185117/original/file-20170907-9538-1uarzku.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/185117/original/file-20170907-9538-1uarzku.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/185117/original/file-20170907-9538-1uarzku.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/185117/original/file-20170907-9538-1uarzku.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The number of sunspots varies over the years, but you’d expect to see more during solar maxima and fewer during solar minima.</span>
<span class="attribution"><a class="source" href="http://www.swpc.noaa.gov/products/goes-x-ray-flux">NOAA</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>We’re heading into the bottom of solar minimum, when the sun tends to have fewer sunspots, <a href="https://www.nasa.gov/content/goddard/the-difference-between-flares-and-cmes">solar flares</a> and <a href="http://www.swpc.noaa.gov/phenomena/coronal-mass-ejections">coronal mass ejections</a> – large <a href="http://earthsky.org/space/what-are-coronal-mass-ejections">expulsions of plasma, electrons and ions, and magnetic fields</a>. But despite where we are in the sun’s cycle, activity on the sun has dramatically picked up over the past few days. On and off, these two sunspots have been flaring and shooting out coronal mass ejections, directed toward Earth.</p>
<p>So what’s going on with the sun? And should we be concerned about this somewhat out-of-character solar behavior?</p>
<h2>Here’s what’s happened so far</h2>
<p>On September 4, the sun started sputtering. A moderately large flare (<a href="https://www.nasa.gov/mission_pages/sunearth/news/classify-flares.html">classified as an M5.5</a>) erupted at approximately 18:30 UTC. It produced a coronal mass ejection aimed at Earth.</p>
<p>The sun continued to flare on September 5. A <a href="https://helios.gsfc.nasa.gov/sep.html">solar energetic particle</a> event from the previous day’s activity arrived at the Earth, where it likely affected radio communications as well as the health of satellite systems.</p>
<p>On September 6, the sun produced two massive <a href="https://www.nasa.gov/mission_pages/sunearth/news/X-class-flares.html">X-class flares</a>. This is the category for the strongest of all solar flares.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"905456884911661057"}"></div></p>
<p>NASA announced one was <a href="https://www.nasa.gov/feature/goddard/2017/active-region-on-sun-continues-to-emits-solar-flares">the most powerful since at least 2008</a>. It <a href="https://twitter.com/NASASun/status/905822026488619008">produced another coronal mass ejection</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/185122/original/file-20170907-9542-wyifki.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/185122/original/file-20170907-9542-wyifki.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/185122/original/file-20170907-9542-wyifki.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/185122/original/file-20170907-9542-wyifki.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/185122/original/file-20170907-9542-wyifki.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/185122/original/file-20170907-9542-wyifki.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/185122/original/file-20170907-9542-wyifki.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/185122/original/file-20170907-9542-wyifki.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The second and strongest of the two X-class flares on September 6 produced a coronal mass ejection directed at Earth.</span>
<span class="attribution"><span class="source">NOAA</span>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Over the next day, the same sunspots continued to spit out more solar flares. It took about an hour for the <a href="https://helios.gsfc.nasa.gov/sep.html">solar energetic particles</a> they emitted to arrive at Earth. These protons are incredibly fast-moving. They can affect communication systems, typically in the polar regions where they are more likely to enter into the Earth’s atmosphere. As with all increases of radiation in space, they can also affect satellite systems and the health of astronauts. </p>
<p>Early in the morning hours of September 7 in the U.S., that first coronal mass ejection that erupted from the sun three days earlier arrived at Earth. Because of the way its magnetic field aligned with Earth’s, it <a href="http://wdc.kugi.kyoto-u.ac.jp/dst_realtime/201709/index.html">generated only a small geomagnetic storm</a>.</p>
<p>After being detected by spacecraft upstream from Earth in the solar wind, the massive coronal mass ejection from September 6 also hit Earth on the evening of September 7 EDT. Its arrival was a few hours earlier than <a href="http://www.swpc.noaa.gov/products/wsa-enlil-solar-wind-prediction">space weather forecasting agencies</a> around the world predicted.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/185185/original/file-20170907-9603-8u5a2w.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/185185/original/file-20170907-9603-8u5a2w.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/185185/original/file-20170907-9603-8u5a2w.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/185185/original/file-20170907-9603-8u5a2w.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/185185/original/file-20170907-9603-8u5a2w.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/185185/original/file-20170907-9603-8u5a2w.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/185185/original/file-20170907-9603-8u5a2w.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/185185/original/file-20170907-9603-8u5a2w.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Both sunspots are visible on the sun’s surface, as well as the flare in the solar atmosphere.</span>
<span class="attribution"><a class="source" href="https://svs.gsfc.nasa.gov/12706">NASA/GSFC/SDO</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<h2>What other effects will Earth see?</h2>
<p>All this solar activity has already caused a couple of radiation storms in Earth’s high latitude regions that <a href="http://www.swpc.noaa.gov/phenomena/solar-flares-radio-blackouts">blacked out radio communication</a> at certain frequencies. The impacts extended toward the equator and have affected high-frequency communications, including ham radios, which are used in emergency and disaster relief management. Radio fade-out maps from the <a href="http://www.sws.bom.gov.au/HF_Systems/6/2/2">Australian Bureau of Meteorology</a> show that <a href="http://www.swpc.noaa.gov/communities/radio-communications">high-frequency radio communication disruptions</a> have likely occurred in the same areas being pummeled by Hurricane Irma.</p>
<p>There has likely been a <a href="https://www.engadget.com/2017/09/07/a-huge-solar-flare-temporarily-knocked-out-gps-communications/">loss of global navigation system satellite communications</a> in those same areas, but it will take time for the data to be analyzed and for us to gain a full understanding of how this space weather activity has affected those on the ground. The <a href="https://theconversation.com/are-you-a-frequent-flyer-solar-storm-radiation-can-be-harmful-28775">radiation storms</a> may also force flights over the polar regions to reroute to avoid increased radiation exposures for people on board and potential loss of communication and navigation systems for aircraft on these paths. </p>
<p>With the collision of the coronal mass ejection from this X-class flare with Earth come other impacts for the near-Earth space environment. <a href="https://theconversation.com/divert-power-to-shields-the-solar-maximum-is-coming-11228">Geomagnetic storms</a>, like the one currently in progress, are known to wreak havoc on a range of satellite and ground-based communication technologies, as well as <a href="https://theconversation.com/damaging-electric-currents-in-space-affect-earths-equatorial-region-not-just-the-poles-45073">power grids</a>, GPS/GNSS, and orbit predictions of satellites and space debris. It is also very likely to produce dazzling aurora activity as far south as the northern U.S. and Europe in the Northern Hemisphere, and as far north as southern Australia and New Zealand in the Southern Hemisphere. </p>
<p>While scientists and aurora-hunting enthusiasts closely watch the storm’s ongoing effects, others will be bracing for problems and disruptions to the many technological services that will be affected.</p>
<p>We don’t need to worry about this coronal mass ejection being “the big one” – a solar storm direct hit that could cause widespread power blackouts and trigger <a href="https://science.nasa.gov/science-news/science-at-nasa/2014/23jul_superstorm/">as much as US$2 trillion worth of damage</a>, according to a National Academy of Sciences study. But this storm, on the back of this month’s abnormally active space weather, may wind up on the larger end of the scale, and will be the subject of lots of analysis and research.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/185120/original/file-20170907-9568-1nt2u26.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/185120/original/file-20170907-9568-1nt2u26.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/185120/original/file-20170907-9568-1nt2u26.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/185120/original/file-20170907-9568-1nt2u26.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/185120/original/file-20170907-9568-1nt2u26.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/185120/original/file-20170907-9568-1nt2u26.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/185120/original/file-20170907-9568-1nt2u26.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/185120/original/file-20170907-9568-1nt2u26.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Images of the sun during solar cycle 23. You typically see more activity during a solar maximum (2001) than during a minimum (1996 or 2006).</span>
<span class="attribution"><a class="source" href="https://www.nasa.gov/mission_pages/sunearth/science/solarcycle23.html">ESA&NASA/SoHO</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>We don’t yet fully understand everything that is happening. But the activity over the past few days, when the sun should be within its quietest period, shows that significant space weather events are possible at any stage of the 11-year solar cycle.</p>
<p>You can help us study this and other solar storms as a citizen scientist. Sign up for <a href="http://www.aurorasaurus.org/">Aurorasaurus</a> and let us know if you observe aurorae with this event.</p><img src="https://counter.theconversation.com/content/83677/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Alexa Halford receives funding from NASA. </span></em></p><p class="fine-print"><em><span>Brett Carter receives funding from the Australian Research Council. </span></em></p><p class="fine-print"><em><span>Julie Currie receives funding from the Australian Research Council. </span></em></p>At a time in the sun’s cycle when space weather experts expect less solar activity, our star is going bonkers with solar flares and coronal mass ejections. What effects will Earth feel?Alexa Halford, Researcher in Physics and Astronomy, Dartmouth CollegeBrett Carter, Senior Research Fellow, RMIT UniversityJulie Currie, Research Officer, RMIT UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/766012017-04-24T13:18:35Z2017-04-24T13:18:35ZCitizen scientists discover new type of aurora<figure><img src="https://images.theconversation.com/files/166480/original/file-20170424-25594-14gpl50.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The aurora Steve.</span> <span class="attribution"><a class="source" href="https://www.facebook.com/photo.php?fbid=10154330305806962&set=oa.1687595721257106&type=3&theater">Rémi Farvacque/Alberta Aurora Chasers (facebook)</a></span></figcaption></figure><p>A collaboration between aurora-hunting citizen scientists and a team of professional researchers has resulted in the discovery of a completely new type of aurora. The finding was made possible thanks to photos taken by aurora enthusiasts from across the globe which scientists could then compare with data from satellites.</p>
<p>The aurora, more commonly known as the <a href="https://theconversation.com/the-southern-lights-put-on-a-display-in-the-night-sky-28612">northern or southern lights</a>, form when electrically charged particles collide with the gases in our upper atmosphere. These charged particles, which have been accelerated into our atmosphere by the Earth’s magnetic field, transfer their energy to the atmospheric gases (such as nitrogen and oxygen). This extra energy is then released in the form of light which gives us the majestic aurora. </p>
<p>The aurora varies in strength depending on how active the sun is. Normally, an aurora is only visible near the magnetic poles but, when particularly active, it can be seen from <a href="https://theconversation.com/what-caused-those-spectacular-northern-lights-and-how-you-can-catch-them-next-time-39081">much further away</a>. </p>
<p>We generally see the aurora as a band about the poles (known as the auroral oval). This band is often green, with tinges of red or purple thrown into the mix. But sightings of this new phenomenon were different – straight away people noticed it didn’t look like the “normal” aurora.</p>
<p>When pictures first starting appearing on <a href="https://www.facebook.com/groups/AlbertaAuroraChasers/">social media</a>, the odd aurora was widely assumed to be what is known as a “<a href="http://news.spaceweather.com/protonarc/">proton arc</a>”, but scientists knew that <a href="https://www.facebook.com/musubk/posts/10100459063136322">this wasn’t right</a>. Proton arcs are caused by protons (positively charged particles which make up the atomic nucleus along with neutrons) colliding with neutral gases in the atmosphere. <a href="https://wiki.oulu.fi/display/SpaceWiki/Proton+aurora">Proton aurora</a> are not visible by eye and are broad and diffuse. This new type of aurora, however, was visible by eye and was a bright, structured band of purple in the night sky. They knew it had to be something else – but what?</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/166469/original/file-20170424-27254-e1icsn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/166469/original/file-20170424-27254-e1icsn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=750&fit=crop&dpr=1 600w, https://images.theconversation.com/files/166469/original/file-20170424-27254-e1icsn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=750&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/166469/original/file-20170424-27254-e1icsn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=750&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/166469/original/file-20170424-27254-e1icsn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=943&fit=crop&dpr=1 754w, https://images.theconversation.com/files/166469/original/file-20170424-27254-e1icsn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=943&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/166469/original/file-20170424-27254-e1icsn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=943&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Meet Steve, the bright purple band reflected in the lake.</span>
<span class="attribution"><span class="source">Dave Markel Photography, ESA</span></span>
</figcaption>
</figure>
<p>The <a href="http://aurorasaurus.org/">Aurorasaurus</a> citizen science project issued a call to arms to collect sightings of this as-yet-unnamed aurora. <a href="http://blog.aurorasaurus.org/?p=449">Over 50 sightings</a> from countries including Canada, US, UK and New Zealand were reported during 2016 and 2017. Because this type of aurora didn’t yet have a name, the citizen scientists called it “Steve” (after the animated children’s film, <a href="http://www.dreamworksanimation.com/oth/">Over the Hedge</a>).</p>
<p>The <a href="http://www.esa.int/Our_Activities/Observing_the_Earth/Swarm/When_Swarm_met_Steve">biggest breakthrough</a> in identifying “Steve” came when Eric Donovan, an associate professor of physics and astronomy at the University of Calgary in Canada, found an instance where a photo was taken of “Steve” at the same time as one of the European Space Agency’s <a href="http://www.esa.int/Our_Activities/Observing_the_Earth/Swarm">Swarm satellites</a> passed above it. Donovan found that as the satellite flew straight though Steve, data from the electric field instrument showed very clear changes.</p>
<figure>
<iframe src="https://player.vimeo.com/video/166121341" width="500" height="281" frameborder="0" webkitallowfullscreen="" mozallowfullscreen="" allowfullscreen=""></iframe>
<figcaption><span class="caption">Steve appears as a purple band (left of video). ‘Normal’ aurora appears as green (right of video).</span></figcaption>
</figure>
<p>Speaking at a recent <a href="https://livestream.com/ESA/earthexplorer2017/videos/152430872">scientific conference</a>, Donovan said that “the temperature 300km above Earth’s surface jumped by 3000°C and the data revealed a 25km-wide ribbon of gas flowing westwards at about 6km per second compared to a speed of about ten metres per second either side of the ribbon.”</p>
<p>This result definitively proved that “Steve” is in fact a distinct feature from the normal aurora oval, as the ribbon was located south of the main aurora. It also showed that “Steve” is not a proton arc.</p>
<p>While we have now been able to measure “Steve”, we still aren’t sure what causes it. It seems that “Steve” is fairly common but it took the power of citizen science for it to really be noticed. Donovan says that research is still ongoing but that he thinks <a href="http://gizmodo.com/what-the-hell-is-this-beautiful-thing-1794528895">he is close to finding the cause</a>.</p>
<p>Discoveries of new types of aurora are rare and this one highlights the importance of citizen scientists. If it weren’t for the dedication of amateur aurora hunters, we may never have started studying this new phenomenon. So if you think you’ve spotted “Steve”, make sure you <a href="http://aurorasaurus.org">submit your sighting</a> to Aurorasaurus to help us learn more about this beautiful purple streak.</p><img src="https://counter.theconversation.com/content/76601/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Nathan Case receives funding from the Science and Technology Facilities Council. This article does not reflect the views of the UK research councils. Nathan is a member of the AuroraWatch UK team at Lancaster University which issues alerts of potential aurora visibility from the UK.</span></em></p>Scientists still don’t know what caused the mysterious phenomenon ‘Steve’.Nathan Case, Senior Research Associate in Space and Planetary Physics, Lancaster UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/724362017-02-03T16:10:22Z2017-02-03T16:10:22ZDon’t panic: the northern lights won’t be turning off anytime soon<figure><img src="https://images.theconversation.com/files/155455/original/image-20170203-13995-1ap4x0d.jpg?ixlib=rb-1.1.0&rect=308%2C0%2C3217%2C2070&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Truly spectacular.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/aigle_dore/9997815384/">Moyan Brenn/flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>The northern lights are nature’s very own magnificent light show. They are the mesmerising end result of electrically charged particles from the sun colliding with the Earth’s upper atmosphere. Though more frequently witnessed from the polar regions, the UK and other places on similar latitudes are lucky enough for the aurora borealis to <a href="https://theconversation.com/what-caused-those-spectacular-northern-lights-and-how-you-can-catch-them-next-time-39081">occasionally grace their night sky</a>. </p>
<p>But <a href="http://www.bbc.co.uk/news/uk-scotland-highlands-islands-38156621">recent reports</a> now claim the phenomenon may no longer be visible from places such as the UK – instead confined to the North Pole. But is this correct? </p>
<p>The northern lights are driven by activity on the sun and the sun’s activity waxes and wanes over an 11-year period known as a solar cycle. The number of large-scale aurora events, the type that is visible from places such as the UK, <a href="https://theconversation.com/make-the-most-of-the-amazing-aurora-borealis-your-next-chance-might-be-a-decade-away-23848">tends to follow this cycle</a>. But each solar cycle is different, with the maximum and minimum activity varying between each cycle. </p>
<h2>Predicting solar activity</h2>
<p><a href="http://nam2015.org/index.php/press-releases/64-irregular-heartbeat-of-the-sun-driven-by-double-dynamo">Current predictions</a> suggest that we are headed for a period of particularly weak solar cycles, where the solar maximum of each cycle will not result in much solar activity. We call this a grand solar minimum.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/155451/original/image-20170203-14016-42fdoy.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/155451/original/image-20170203-14016-42fdoy.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/155451/original/image-20170203-14016-42fdoy.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=250&fit=crop&dpr=1 600w, https://images.theconversation.com/files/155451/original/image-20170203-14016-42fdoy.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=250&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/155451/original/image-20170203-14016-42fdoy.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=250&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/155451/original/image-20170203-14016-42fdoy.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=314&fit=crop&dpr=1 754w, https://images.theconversation.com/files/155451/original/image-20170203-14016-42fdoy.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=314&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/155451/original/image-20170203-14016-42fdoy.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=314&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The number of sunspots observed on the sun.</span>
<span class="attribution"><span class="source">Global Warming Art/Wikipedia</span></span>
</figcaption>
</figure>
<p>Grand solar minimums can last for several decades or even centuries and have occurred throughout history. Although solar output does decline during these periods, it doesn’t mean that we are heading for a <a href="https://theconversation.com/no-we-arent-heading-into-a-mini-ice-age-44677">new ice age</a>.</p>
<p>A <a href="http://www.nature.com/articles/srep41548">study recently published in Nature</a> has modelled the perhaps most well-known grand solar minimum, called the “Maunder minimum”. This particular grand solar minimum started in 1645 and finally ended 70 years later. During this time <a href="http://www.stsci.edu/stsci/meetings/lisa3/beckmanj.html">only 50 sunspots</a>, structures on the sun that act as a measure of its activity, were observed. This is compared to the 40,000-50,000 that we would expect during a period of “normal” activity lasting that long.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/155453/original/image-20170203-14022-1qke3zc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/155453/original/image-20170203-14022-1qke3zc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/155453/original/image-20170203-14022-1qke3zc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/155453/original/image-20170203-14022-1qke3zc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/155453/original/image-20170203-14022-1qke3zc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/155453/original/image-20170203-14022-1qke3zc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/155453/original/image-20170203-14022-1qke3zc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/155453/original/image-20170203-14022-1qke3zc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Sunspots (black) visible on the sun.</span>
<span class="attribution"><span class="source">NASA/SDO/AIA/HMI/Goddard Space Flight Center</span></span>
</figcaption>
</figure>
<p>The authors of the study found that during the Maunder minimum, the solar wind, which drives the aurora, dramatically weakened. They also illustrate that as the solar wind weakens, so too will the aurora. </p>
<p>If we are in fact heading into a new grand solar minimum, it stands to reason that we might see less of nature’s beautiful spectacle. But does that mean we’ll stop seeing it from the UK altogether <a href="http://www.dailymail.co.uk/sciencetech/article-4177134/Northern-Lights-stop-appearing-UK.html">as some have suggested</a>?</p>
<h2>Lessons from the past</h2>
<p>Looking back at historical records of aurora sightings might provide the answer. Fortunately, a <a href="http://www.aanda.org/articles/aa/full_html/2015/09/aa26652-15/aa26652-15.html">study</a> has done just that. The authors analysed auroral observations during two grand solar minimums– including the Maunder minimum. They found that the number of aurora sightings from below 56° magnetic latitude (which is similar to geographic latitude but measured from the magnetic pole rather than the geographic pole) did indeed decrease. But they did not stop altogether. </p>
<p>That value of 56° magnetic latitude is actually quite important as it happens to coincide with the magnetic latitude of the UK (more specifically somewhere close to Lancaster, England).</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/155456/original/image-20170203-14031-b1av9m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/155456/original/image-20170203-14031-b1av9m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/155456/original/image-20170203-14031-b1av9m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=300&fit=crop&dpr=1 600w, https://images.theconversation.com/files/155456/original/image-20170203-14031-b1av9m.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=300&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/155456/original/image-20170203-14031-b1av9m.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=300&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/155456/original/image-20170203-14031-b1av9m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=377&fit=crop&dpr=1 754w, https://images.theconversation.com/files/155456/original/image-20170203-14031-b1av9m.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=377&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/155456/original/image-20170203-14031-b1av9m.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=377&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The aurora captured from Groomsport, Northern Ireland (UK).</span>
<span class="attribution"><span class="source">Philip McErlean/flickr</span></span>
</figcaption>
</figure>
<p>So what’s my prediction for the aurora over the next century? If the models are correct and we do head into a grand solar minimum, then solar activity is going to decrease – and remain at very low levels for decades to come. With this decrease in solar activity, aurora sightings from outside the polar regions are going to become rarer. But that doesn’t necessarily mean they’ll stop altogether. It also isn’t certain that we are heading for a grand solar minimum or – even if we are – when it might occur. </p>
<p>So while that elusive light show might get even more elusive, don’t fret just yet: the northern lights aren’t going out anytime soon.</p><img src="https://counter.theconversation.com/content/72436/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Nathan Case receives funding from the Science and Technology Facilities Council. Nathan is a member of the AuroraWatch UK team at Lancaster University which issues alerts of potential aurora visibility from the UK.</span></em></p>Historical records can help us understand what will happen to the northern lights.Nathan Case, Senior Research Associate in Space and Planetary Physics, Lancaster UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/681882016-11-04T12:09:05Z2016-11-04T12:09:05ZBeautiful green ‘airglow’ spotted by aurora hunters – but what is it?<figure><img src="https://images.theconversation.com/files/144409/original/image-20161103-25353-1kljd9q.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Nighttime panorama showing Pakistan’s Indus River valley, taken from space. The green band above the horizon is airglow.</span> <span class="attribution"><a class="source" href="http://earthobservatory.nasa.gov/IOTD/view.php?id=86725">NASA Earth Observatory</a></span></figcaption></figure><p>Amateur astronomers and aurora hunters alike have been reporting a green glow across the UK sky. Easily confused with the <a href="https://theconversation.com/what-caused-those-spectacular-northern-lights-and-how-you-can-catch-them-next-time-39081">aurora borealis</a>, or northern lights, the sightings were of another phenomena called “airglow”.</p>
<p>Airglow is the natural “glowing” of the Earth’s atmosphere. It happens all the time and across the whole globe. There are three types of airglow: dayglow, twilightglow and nightglow. Each is the result of sunlight interacting with the molecules in our atmosphere, but they have their own special way of forming. </p>
<p>Dayglow forms when sunlight strikes the daytime atmosphere. Some of the sunlight is absorbed by the molecules in the atmosphere, which gives them excess energy. They become excited. The molecules then release this energy as light, either at the same or slightly lower frequency (colour) as the light they absorbed. This light is much dimmer than daylight, so we can’t see it by eye. </p>
<p>Twilight glow is essentially the same as dayglow, but only the upper atmosphere is sunlit. The rest of the atmosphere and the observer on the ground are in darkness. So, unlike day glow, twilightglow is actually visible to us on the ground with the naked eye.</p>
<h2>Chemiluminescence</h2>
<p>The chemistry behind nightglow is different. There is no sunlight shining on the nighttime atmosphere. Instead, a process called “chemiluminescence” is responsible for the glowing atmosphere.</p>
<p>Sunlight deposits energy into the atmosphere during the day, some of which is transferred to oxygen molecules (e.g. O₂). This extra energy causes the oxygen molecules to rip apart into individual oxygen atoms. This happens particularly around 100km in altitude. However, atomic oxygen isn’t able to get rid of this excess energy easily and so acts as a “store” of energy for several hours. </p>
<p>Eventually the atomic oxygen does manage to “recombine”, once again forming molecular oxygen. The molecular oxygen then releases energy, again in the form of light. Several different colours are produced, including a “bright” green emission. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/144553/original/image-20161104-25319-1ppkbdl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/144553/original/image-20161104-25319-1ppkbdl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=267&fit=crop&dpr=1 600w, https://images.theconversation.com/files/144553/original/image-20161104-25319-1ppkbdl.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=267&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/144553/original/image-20161104-25319-1ppkbdl.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=267&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/144553/original/image-20161104-25319-1ppkbdl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=336&fit=crop&dpr=1 754w, https://images.theconversation.com/files/144553/original/image-20161104-25319-1ppkbdl.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=336&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/144553/original/image-20161104-25319-1ppkbdl.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=336&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Airglow spotted in panoramic shot of the Very Large Telescope.</span>
<span class="attribution"><span class="source">ESO/Y. Beletsky - http://www.eso.org/public/images/uhd_vlts_pan_cc/</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>In reality, the green nightglow isn’t particularly bright, it’s just the brightest of all nightglow emissions. <a href="https://theconversation.com/new-atlas-shows-extent-of-light-pollution-what-does-it-mean-for-our-health-60836">Light pollution</a> and cloudy skies will prevent sightings. If you’re lucky though, you might just be able to see it by eye or capture it on long-exposure photos.</p>
<h2>Not to be confused with aurora</h2>
<p>The green night glow emission is very similar to the famous green <a href="https://theconversation.com/what-caused-those-spectacular-northern-lights-and-how-you-can-catch-them-next-time-39081">we see in the northern lights</a>. This is unsurprising since it is produced by the same oxygen molecules as the green aurora. But the two phenomena are not related.</p>
<p>Aurora form when charged particles, such as electrons, bombard the Earth’s atmosphere. These charged particles, which started off at the sun and were accelerated in the <a href="https://theconversation.com/what-makes-one-earth-like-planet-more-habitable-than-another-33479">Earth’s magnetosphere</a>, collide with the atmospheric gases. They transfer energy, forcing the gases to emit light.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/144453/original/image-20161103-25353-c3ux4n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/144453/original/image-20161103-25353-c3ux4n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/144453/original/image-20161103-25353-c3ux4n.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/144453/original/image-20161103-25353-c3ux4n.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/144453/original/image-20161103-25353-c3ux4n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/144453/original/image-20161103-25353-c3ux4n.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/144453/original/image-20161103-25353-c3ux4n.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The aurora and airglow captured from the International Space Station.</span>
<span class="attribution"><span class="source">NASA</span></span>
</figcaption>
</figure>
<p>But it isn’t just the process behind them that is different. The aurora form in a ring around the magnetic poles (known as the auroral oval); whereas nightglow is emitted across the whole night sky. The aurora are very structured (due to the Earth’s magnetic field); whereas airglow is generally quite uniform. The extent of the aurora is affected by the strength of the solar wind; whereas airglow happens all the time.</p>
<p>Why then did we get a lot sightings from the UK recently, rather than all the time? The brightness of airglow correlates with the level of ultraviolet (UV) light being emitted from the sun – which varies over time. The time of year also seems to have an impact on the strength of airglow.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/144560/original/image-20161104-25362-yjymly.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/144560/original/image-20161104-25362-yjymly.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=397&fit=crop&dpr=1 600w, https://images.theconversation.com/files/144560/original/image-20161104-25362-yjymly.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=397&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/144560/original/image-20161104-25362-yjymly.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=397&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/144560/original/image-20161104-25362-yjymly.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=499&fit=crop&dpr=1 754w, https://images.theconversation.com/files/144560/original/image-20161104-25362-yjymly.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=499&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/144560/original/image-20161104-25362-yjymly.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=499&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Airglow captured by Michael Darby from Cornwall, UK. The Milky Way shines through in the centre of the image.</span>
<span class="attribution"><span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>To maximise your chances of spotting airglow, you’ll want to take a long-exposure photograph of a clear, dark, night sky. Airglow can be spotted in any direction that is free of light pollution, at about 10⁰-20⁰ above the horizon.</p><img src="https://counter.theconversation.com/content/68188/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Nathan Case receives funding from the Science and Technology Facilities Council. Nathan is a member of the AuroraWatch UK team at Lancaster University which issues alerts of potential aurora visibility from the UK.</span></em></p>Here’s how to tell airglow from northern lights.Nathan Case, Senior Research Associate in Space and Planetary Physics, Lancaster UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/631292016-07-27T17:06:11Z2016-07-27T17:06:11ZThe power of Jupiter’s Great Red Spot: enormous storm may be heating the atmosphere<figure><img src="https://images.theconversation.com/files/132168/original/image-20160727-5643-1bbrbk4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">NASA</span></span></figcaption></figure><p>There is an “energy crisis” on Jupiter. At 800K (527ºC), its upper atmosphere is 600 degrees hotter than expected – a phenomenon also seen on the other giant planets in our solar system. And to make the matter even more perplexing, researchers have now discovered that the region of the atmosphere above Jupiter’s Great Red Spot, a giant storm system, is hundreds of degrees hotter than anywhere else on the planet.</p>
<p>If heat from the sun isn’t enough to produce these temperatures, where does the energy come from? The new observations, <a href="http://nature.com/articles/doi:10.1038/nature18940">published in Nature</a>, suggest that Jupiter’s interior, rather than outside radiation, could be responsible.</p>
<p>Jupiter is a giant gas planet. From Earth we see zones and belts of clouds suspended in the hydrogen-rich atmosphere rotating with respect to each other, with the enormous Great Red Spot in the southern hemisphere. This storm is 22,000km by 12,000km. Though a mere pimple on Jupiter, it would engulf the Earth, and has been raging for hundreds of years, though now it <a href="https://theconversation.com/from-great-red-spot-to-orange-pimple-is-jupiters-superstorm-finally-blowing-over-49318">seems to be slowly shrinking</a>. </p>
<p>If you move in towards the planet, the pressure and temperature of the atmosphere increases and eventually becomes metallic hydrogen at a distance up that is about half Jupiter’s radius. Jupiter emits about 60% more power than it receives from sunlight. This is likely due to the helium rain (which doesn’t dissolve in metallic hydrogen) that falls from the top of Jupiter’s highly compressed metallic hydrogen layer towards the centre of the planet, which generates kinetic energy. So we know the inside of Jupiter is extremely hot. </p>
<p>Motions in the metallic hydrogen layer also create Jupiter’s huge magnetic field. This field diverts solar wind around the planet, and the sulphurous material <a href="http://www.space.com/16419-io-facts-about-jupiters-volcanic-moon.html">spewing from the volcanoes on Io</a>, one of Jupiter’s moons, dominates the magnetosphere. Because Jupiter rotates rapidly in just under ten hours, the whole magnetosphere is driven by the rotation and it bulges at the equator. Jupiter has its own aurora (northern and southern lights), powered mainly by the magnetosphere. This is seen mainly in the ultraviolet, but with a small contribution (seen in X-rays) from the solar wind. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/132221/original/image-20160727-21578-1t9fwik.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/132221/original/image-20160727-21578-1t9fwik.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/132221/original/image-20160727-21578-1t9fwik.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/132221/original/image-20160727-21578-1t9fwik.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/132221/original/image-20160727-21578-1t9fwik.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/132221/original/image-20160727-21578-1t9fwik.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/132221/original/image-20160727-21578-1t9fwik.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Jupiter’s magnetosphere and aurora.</span>
<span class="attribution"><a class="source" href="http://apod.nasa.gov/apod/ap160406.html">NASA, ESA, Chandra, Hubble</a></span>
</figcaption>
</figure>
<p>As at all planets, the aurora provides a heat source from above. But this energy input is concentrated in the polar regions and cannot explain the heating of the upper atmosphere over all latitudes.</p>
<h2>Strong evidence</h2>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/132223/original/image-20160727-21564-15b6cap.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/132223/original/image-20160727-21564-15b6cap.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/132223/original/image-20160727-21564-15b6cap.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=392&fit=crop&dpr=1 600w, https://images.theconversation.com/files/132223/original/image-20160727-21564-15b6cap.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=392&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/132223/original/image-20160727-21564-15b6cap.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=392&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/132223/original/image-20160727-21564-15b6cap.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=492&fit=crop&dpr=1 754w, https://images.theconversation.com/files/132223/original/image-20160727-21564-15b6cap.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=492&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/132223/original/image-20160727-21564-15b6cap.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=492&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Artist’s impression of acoustic waves from Jupiter’s Great Red Spot.</span>
<span class="attribution"><span class="source">Karen Teramura, UH IfA, James O’Donoghue</span></span>
</figcaption>
</figure>
<p>The new study is based on observations of an ion known as <a href="http://chemistry.stackexchange.com/questions/17218/how-is-bonding-in-the-trihydrogen-cation-and-triatomic-hydrogen-possible">trihydrogen cation</a>, which can be used to estimate the temperature in hydrogen-rich atmospheres. This indicates that the highest temperatures of the planet, by some 800 degrees, are 500 miles straight above the Great Red Spot. The temperatures in the polar regions are also slightly elevated compared with the rest.</p>
<p>Because the Great Red Spot is at lower altitude in Jupiter’s atmosphere, this strongly suggests that energy travelling upwards from the planet’s hot interior is somehow enhanced by the raging storm. The researchers suggest that the storm is producing acoustic waves, which are simply compressions of air, that transport the energy upwards like a huge, high-powered loudspeaker. </p>
<p>But what about the high temperatures at other latitudes, which are still about 600 degrees higher than models would predict? It <a href="http://adsabs.harvard.edu/abs/2001DPS....33.2201S">has been suggested</a> previously that acoustic waves across the planet – produced by turbulent motion in the counter-rotating zones and belts and by smaller more widespread storms – could also be heating the atmosphere. As now there is a direct observation that exactly this happens in the region around the Great Red Spot, it makes sense that it could take place over all latitudes. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/WZwNYiGReDg?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Bright regions at the poles result from auroral emissions. Great Red Spot emissions at mid-latitudes can be seen moving under the slit from left to right.</span></figcaption>
</figure>
<p>In fact, there are examples on Earth where such energy transfer happens to high altitudes over the Andes mountains, so it seems plausible that something similar could happen on Jupiter. The result could also explain high upper atmosphere temperatures seen at other giant planets and, by analogy, any <a href="https://theconversation.com/uk/topics/exoplanets">exoplanets</a> with turbulent atmospheres. </p>
<p>The <a href="https://theconversation.com/nasas-juno-arrives-at-jupiter-to-lift-cloudy-veil-60879">NASA Juno mission</a>, recently arrived at Jupiter and will tell us more about Jupiter’s interior structure and its aurora, as well as its formation. But we may need to wait for the <a href="http://sci.esa.int/juice/">ESA JUICE mission</a> which arrives in 2030 to tell us more detail about the equatorial regions to help solve Jupiter’s energy crisis for sure.</p><img src="https://counter.theconversation.com/content/63129/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Andrew Coates receives funding from STFC and UK Space Agency</span></em></p>New research solves enigma of strange hotspots in Jupiter’s atmosphere.Andrew Coates, Professor of Physics, Deputy Director (Solar System) at the Mullard Space Science Laboratory, UCLLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/503412015-11-09T15:16:50Z2015-11-09T15:16:50ZWhat’s it like to see auroras on other planets?<figure><img src="https://images.theconversation.com/files/101275/original/image-20151109-29341-pe4xmd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Aalto University</span></span></figcaption></figure><p>Witnessing an aurora first-hand is a truly awe-inspiring experience. The natural beauty of the northern or southern lights captures the public imagination unlike any other aspect of space weather. But auroras aren’t unique to Earth and can be seen on several other planets in our solar system.</p>
<p><a href="https://theconversation.com/what-caused-those-spectacular-northern-lights-and-how-you-can-catch-them-next-time-39081">An aurora</a> is the impressive end result of a series of events that starts at the sun. The sun constantly emits a stream of charged particles known as the solar wind into the depths of the solar system. When these particles reach a planet, such as Earth, they interact with the magnetic field surrounding it (the magnetosphere), compressing the field into a teardrop shape and transferring energy to it.</p>
<p>Because of the way the lines of a magnetic field can change, the charged particles inside the magnetosphere can then be accelerated into the upper atmosphere. Here they collide with molecules such as nitrogen and oxygen, giving off energy in the form of light. This creates a ribbon of colour that can be seen across the sky close to the planet’s magnetic north and south poles – this is the aurora.</p>
<h2>Gas giant auroras</h2>
<p>Using measurements from spacecraft, such as <a href="http://www.esa.int/Our_Activities/Space_Science/Cassini-Huygens">Cassini</a>, or images from telescopes, such as the <a href="http://hubblesite.org/">Hubble Space Telescope</a>, space physicists have been able to verify that some of our closest neighbours have their own auroras. Scientists do this by studying the electromagnetic radiation received from the planets, and certain wavelength emissions are good indicators of the presence of auroras.</p>
<p>Each of the gas giants (Jupiter, Saturn, Uranus, and Neptune) has a strong magnetic field, a dense atmosphere and, as a result, its own aurora. The exact nature of these auroras is slightly different from Earth’s, since their atmospheres and magnetospheres are different. The colours, for example, depend on the gases in the planet’s atmosphere. But the fundamental idea behind the auroras is the same.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/101276/original/image-20151109-29326-1md6x8a.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/101276/original/image-20151109-29326-1md6x8a.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=342&fit=crop&dpr=1 600w, https://images.theconversation.com/files/101276/original/image-20151109-29326-1md6x8a.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=342&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/101276/original/image-20151109-29326-1md6x8a.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=342&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/101276/original/image-20151109-29326-1md6x8a.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=430&fit=crop&dpr=1 754w, https://images.theconversation.com/files/101276/original/image-20151109-29326-1md6x8a.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=430&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/101276/original/image-20151109-29326-1md6x8a.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=430&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Blue aurora on Jupiter.</span>
<span class="attribution"><span class="source">NASA/J Clarke</span></span>
</figcaption>
</figure>
<p>For example, several of Jupiter’s moons, including Io, Ganymede and Europa, affect the blue aurora created by the solar wind. Io, which is just a little larger than our own moon, is volcanic and spews out vast amounts of charged particles into Jupiter’s magnetosphere, <a href="http://www.space.com/29248-jupiter-auroras-volcanic-moon-io.html">producing large electrical currents</a> and bright ultraviolet (UV) aurora.</p>
<p>On Saturn, the strongest auroras are in the UV and infrared bands of the colour spectrum and so would not be visible to the human eye. But weaker (and rarer) pink and purple auroras <a href="http://www.sciencedirect.com/science/article/pii/S0019103515002328">have also been spotted</a>.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/101162/original/image-20151108-16255-11oqoqm.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/101162/original/image-20151108-16255-11oqoqm.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=591&fit=crop&dpr=1 600w, https://images.theconversation.com/files/101162/original/image-20151108-16255-11oqoqm.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=591&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/101162/original/image-20151108-16255-11oqoqm.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=591&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/101162/original/image-20151108-16255-11oqoqm.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=743&fit=crop&dpr=1 754w, https://images.theconversation.com/files/101162/original/image-20151108-16255-11oqoqm.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=743&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/101162/original/image-20151108-16255-11oqoqm.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=743&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Hubble Space Telescope captures Saturn’s aurora.</span>
<span class="attribution"><span class="source">NASA/ESA/Hubble</span></span>
</figcaption>
</figure>
<p>Mercury also has a magnetosphere and so we might expect aurora there too. Unfortunately, Mercury is too small and too close to the sun for it to retain an atmosphere, meaning the planet doesn’t have any molecules for the solar wind to excite and that means no auroras.</p>
<h2>The unexpected auroras</h2>
<p>On Venus and Mars, the story is different. While neither of these planets has a large-scale magnetic field, both have an atmosphere. As the solar wind interacts with the Venusian ionosphere (the layer of the atmosphere with the most charged particles), it actually creates or induces a magnetic field. Using data from the <a href="http://www.esa.int/Our_Activities/Space_Science/Venus_Express">Venus Express</a> spacecraft, <a href="http://www.sciencemag.org/content/336/6081/567">scientists found</a> that this magnetic field stretches out away from the sun to form a “magnetotail” that redirects accelerated particles into the atmosphere and forms an aurora.</p>
<p><a href="https://theconversation.com/how-did-mars-lose-its-habitable-climate-the-answer-is-blowing-in-the-solar-wind-50258">Mars’s atmosphere is too thin</a> for a similar process to occur there, but it still has aurora created by localised magnetic fields embedded in the planet’s crust. These are the remnants of a much larger, global magnetic field that disappeared as the planet’s core cooled. Interaction between the solar wind and the Martian atmosphere generates “discrete” auroras that are confined to the regions of crustal field. </p>
<p>A [recent discovery]([(https://theconversation.com/how-did-mars-lose-its-habitable-climate-the-answer-is-blowing-in-the-solar-wind-50258) by the <a href="https://www.nasa.gov/mission_pages/maven/main/index.html">MAVEN mission</a> showed that Mars also has much larger auroras spread across the northern hemisphere, and probably the whole planet too. This “diffuse” aurora is the result of solar energetic particles raining into the Martian atmosphere, rather than particles from the solar wind interacting with a magnetic field.</p>
<p>If an astronaut were to stand on the surface of Mars, they might still see an aurora but it would likely be rather faint and blue, and, unlike on Earth, not be necessarily near the planet’s poles.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/101272/original/image-20151109-29333-u6cfas.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/101272/original/image-20151109-29333-u6cfas.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/101272/original/image-20151109-29333-u6cfas.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/101272/original/image-20151109-29333-u6cfas.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/101272/original/image-20151109-29333-u6cfas.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/101272/original/image-20151109-29333-u6cfas.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/101272/original/image-20151109-29333-u6cfas.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Brown dwarf with red aurora.</span>
<span class="attribution"><span class="source">Chuck Carter and Gregg Hallinan/Caltech</span></span>
</figcaption>
</figure>
<p>Most planets outside our solar system are too dim compared to their parent star for us to see if they have auroras. But scientists <a href="http://www.nature.com/nature/journal/v523/n7562/full/nature14619.html">recently discovered</a> a brown dwarf (an object bigger than a planet but not big enough to burn like a star) 18 light years from Earth that is believed to have a bright red aurora. This raises the possibility of discovering other exoplanets with atmospheres and magnetic fields that have their own auroras.</p>
<p>Such discoveries are exciting and beautiful, but they are also scientifically useful. Investigating auroras gives scientists tantalising clues about a planet’s magnetic and particle environment and could further our understanding of how charged particles and magnetic fields interact. This could even unlock the answers to other physics problems, <a href="http://news.mit.edu/2010/fusion-ldx-0125">such as nuclear fusion</a>.</p><img src="https://counter.theconversation.com/content/50341/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Nathan Case receives funding from the Science and Technology Facilities Council. Nathan is a member of the AuroraWatch UK team at Lancaster University which issues alerts of potential aurora visibility from the UK.</span></em></p>Recent Martian findings are just the latest discoveries of aurora on other planets, both in and out of our solar system.Nathan Case, Senior Research Associate in Space and Planetary Physics, Lancaster UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/462402015-09-18T10:03:34Z2015-09-18T10:03:34ZScientists at work: space balloons and charged particles above the Arctic Circle<figure><img src="https://images.theconversation.com/files/94869/original/image-20150915-29648-1c9ly8v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Launching a space balloon in Sweden.</span> <span class="attribution"><span class="source">Alexa Halford</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><p>I research space weather. That’s how physicists describe how <a href="https://www.nasa.gov/mission_pages/sunearth/news/storms-on-sun.html#.VfBiw7RVOAV">storms on the sun end up affecting us</a> here on Earth. Most days I sit at a computer coding, attending telephone conference meetings with collaborators across the country and meeting with fellow space physicists. But sprinkled throughout the year I get to do exciting fieldwork in remote locations. We launch high-tech space balloons in an effort to help untangle what happens when charged particles from solar storms hit the Earth’s magnetic field, called its magnetosphere.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/94576/original/image-20150913-19845-1yz5lb2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/94576/original/image-20150913-19845-1yz5lb2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/94576/original/image-20150913-19845-1yz5lb2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=300&fit=crop&dpr=1 600w, https://images.theconversation.com/files/94576/original/image-20150913-19845-1yz5lb2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=300&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/94576/original/image-20150913-19845-1yz5lb2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=300&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/94576/original/image-20150913-19845-1yz5lb2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=377&fit=crop&dpr=1 754w, https://images.theconversation.com/files/94576/original/image-20150913-19845-1yz5lb2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=377&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/94576/original/image-20150913-19845-1yz5lb2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=377&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Events on the sun can change conditions in near-Earth space.</span>
<span class="attribution"><a class="source" href="http://www.nasa.gov/mission_pages/sunearth/dhs-nasa-space-weather-twitter-chat">NASA</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>I primarily work with the Balloon Array for Radiation-belt Relativistic Electron Losses (<a href="http://www.nasa.gov/mission-pages/rbsp/barrel">BARREL</a>) mission, led by Robyn Millan here at Dartmouth College. We’re investigating the electrons and protons that travel all the way from the sun and then get trapped in the Earth’s magnetic field. Often they stick around, just bouncing and drifting along in our planet’s so-called radiation belts – these are donut-shaped regions rich in charged particles, held in place around Earth by its magnetic field.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/o4ken8pE7OA?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">It’s a team effort to unravel how space weather works – and affects us.</span></figcaption>
</figure>
<p>But during a geomagnetic storm, changes in the Earth’s magnetic field can <a href="http://dx.doi.org/10.1029/2002GL016513">accelerate and transport</a> these electrons and protons. They can wind up getting “lost”: shot out of the radiation belts back into space or down into our atmosphere. If they start colliding with neutral, uncharged particles in the atmosphere, that can affect upper atmospheric chemistry – and be bad news for our technology down here on Earth. For example, geomagnetic storms <a href="https://theconversation.com/damaging-electric-currents-in-space-affect-earths-equatorial-region-not-just-the-poles-45073">can cause</a> blackouts, increased corrosion in pipelines, destruction of satellites and a resulting loss of communication connections.</p>
<p>My colleagues and I focus on the radiation belt electrons that get lost to the Earth’s atmosphere. If we can unravel more about what’s happening with them, the hope is we can figure out how to better predict space weather – and its effects on terrestrial weather. Ultimately, with better understanding of what’s going on, we can work on protecting our technology from these geomagnetic squalls.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/ljfa1R9JXWk?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">What is a magnetic field?</span></figcaption>
</figure>
<h2>Magnets all around us</h2>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/94577/original/image-20150913-19845-1of3std.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/94577/original/image-20150913-19845-1of3std.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/94577/original/image-20150913-19845-1of3std.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=403&fit=crop&dpr=1 600w, https://images.theconversation.com/files/94577/original/image-20150913-19845-1of3std.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=403&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/94577/original/image-20150913-19845-1of3std.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=403&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/94577/original/image-20150913-19845-1of3std.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=506&fit=crop&dpr=1 754w, https://images.theconversation.com/files/94577/original/image-20150913-19845-1of3std.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=506&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/94577/original/image-20150913-19845-1of3std.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=506&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The magnetic field of a bar magnet revealed by iron filings on paper.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Magnet0873.png">Newton Henry Black</a></span>
</figcaption>
</figure>
<p>You can think of the Earth as a big bar magnet, like the kind you might have had in your elementary school classroom. You’re probably familiar with magnets’ attractive and repulsive properties. Around a bar magnet, iron shavings trace out what we can think of as lines of magnetic field.</p>
<p>Protons and electrons trapped in Earth’s magnetosphere <a href="http://vanallenprobes.jhuapl.edu/gallery/animations/visualization/ParticleMotionMovie2012.mov">follow these same kinds of lines</a>, converging at the poles. Typically the particles just <a href="http://www.windows2universe.org/glossary/particle_motion.html">gyrate and bounce along these lines</a>, happily drifting around the Earth in those radiation belts. (To get a feel for how the magnetic field lines affect protons and electrons, check out the <a href="http://www.spaceweathercenter.org/interactives/mmg.html">magnetospheric mini golf</a> game.)</p>
<p>Since space is so big, and the density of particles is so small, they can usually travel without bumping into each other. But during geomagnetic activity – like a storm in space – the particles can get pushed farther down the field line, closer to the Earth. In a <a href="http://svs.gsfc.nasa.gov/cgi-bin/details.cgi?aid=20056">process similar to what creates the auroras</a>, they start colliding with the denser atmosphere. And this is when some of the charged particles wind up “lost” from the radiation belts.</p>
<p>What happens to the “lost” particles that seem to disappear in the atmosphere, and why? To answer these questions, we travel to the polar regions to collect data.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/94295/original/image-20150909-18653-ee7t20.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/94295/original/image-20150909-18653-ee7t20.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/94295/original/image-20150909-18653-ee7t20.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=750&fit=crop&dpr=1 600w, https://images.theconversation.com/files/94295/original/image-20150909-18653-ee7t20.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=750&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/94295/original/image-20150909-18653-ee7t20.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=750&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/94295/original/image-20150909-18653-ee7t20.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=943&fit=crop&dpr=1 754w, https://images.theconversation.com/files/94295/original/image-20150909-18653-ee7t20.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=943&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/94295/original/image-20150909-18653-ee7t20.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=943&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Launch of BARREL payload 3B from the SSC’s ESRANGE.</span>
<span class="attribution"><span class="source">Alexa Halford</span></span>
</figcaption>
</figure>
<h2>Polar hunt for solar particles</h2>
<p>This year we headed 90 miles above the Arctic Circle to the <a href="http://www.sscspace.com/launch-services-esrange-space-center">Swedish Space Corporation’s ESRANGE</a> to launch our space balloons. Our goal is to send the balloons up as far as 22 miles (35 km) into the stratosphere to measure X-rays during a geomagnetic storm; since X-rays are created when electrons from the radiation belts interact with uncharged particles in the atmosphere, we can use them to infer when electrons are lost.</p>
<figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/94297/original/image-20150909-18669-7ke99m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/94297/original/image-20150909-18669-7ke99m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=750&fit=crop&dpr=1 600w, https://images.theconversation.com/files/94297/original/image-20150909-18669-7ke99m.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=750&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/94297/original/image-20150909-18669-7ke99m.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=750&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/94297/original/image-20150909-18669-7ke99m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=943&fit=crop&dpr=1 754w, https://images.theconversation.com/files/94297/original/image-20150909-18669-7ke99m.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=943&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/94297/original/image-20150909-18669-7ke99m.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=943&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">BARREL payload.</span>
<span class="attribution"><span class="source">Alexa</span></span>
</figcaption>
</figure>
<p>Each balloon carries a <a href="http://dx.doi.org/10.1002/2014JA020874">payload of scientific equipment</a>. A scintillator counts X-rays. A magnetometer measures the magnetic field of the Earth. Each payload and balloon has its own GPS tracker. </p>
<p>During our last campaigns in Antarctica, we were flying during a period of circumpolar winds that blow long and hard in a circle around the poles. This allowed our 300,000-cubic-foot balloons to stay up, on average, for 12 days. This year in Sweden, though, we flew during a period called “turnaround,” when the stratospheric winds are changing direction, and our flights were lucky to last even four hours.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/KWmDNcKw70I?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">BARREL balloons fly in Antarctica.</span></figcaption>
</figure>
<p>When the balloon either starts falling below an altitude of 13.6 miles (22 km), or starts moving toward too densely populated regions, we have to terminate – that is, pop – the balloon. The balloon and the payload then separately fall back to Earth.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/94310/original/image-20150909-18645-sd4hyp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/94310/original/image-20150909-18645-sd4hyp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/94310/original/image-20150909-18645-sd4hyp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/94310/original/image-20150909-18645-sd4hyp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/94310/original/image-20150909-18645-sd4hyp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/94310/original/image-20150909-18645-sd4hyp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/94310/original/image-20150909-18645-sd4hyp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/94310/original/image-20150909-18645-sd4hyp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Retrieval of the balloon from the launch of BARREL payload 3C. It was a short 500 meters from the road and less than an hour drive from ESRANGE.</span>
<span class="attribution"><span class="source">Alexa Halford</span></span>
</figcaption>
</figure>
<p>When our BARREL balloons flew in Antarctica, we weren’t able to recover most of them because the terrain was so difficult to cross. This year in Sweden we were able to recover all the payloads. When they came down close to the launch base, we drove out and hiked through bogs and woods to retrieve payloads and balloons.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/94309/original/image-20150909-18653-176ub90.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/94309/original/image-20150909-18653-176ub90.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/94309/original/image-20150909-18653-176ub90.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=480&fit=crop&dpr=1 600w, https://images.theconversation.com/files/94309/original/image-20150909-18653-176ub90.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=480&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/94309/original/image-20150909-18653-176ub90.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=480&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/94309/original/image-20150909-18653-176ub90.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=603&fit=crop&dpr=1 754w, https://images.theconversation.com/files/94309/original/image-20150909-18653-176ub90.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=603&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/94309/original/image-20150909-18653-176ub90.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=603&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">We spotted the payload and its orange parachute via helicopter before finding and retrieving it and its balloon.</span>
<span class="attribution"><span class="source">Alexa Halford</span></span>
</figcaption>
</figure>
<p>When they flew a bit farther away (like into Norway or Finland), we had to rent a helicopter to travel out and pick them up.</p>
<p>During the campaign, when we’re launching the balloons, we’re in constant contact with the instrument teams on NASA’s <a href="http://vanallenprobes.jhuapl.edu">Van Allen Probes</a> as well as other satellite missions. We work together, trying to predict when satellites will be lined up along the same magnetic field lines with the balloons. That way we can look at high-resolution data the satellites are collecting in space on the same magnetic field lines at the same time our balloons are flying. We want to make links between space conditions and our X-ray readings, which stand in for how many electrons are being lost to the atmosphere.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/94304/original/image-20150909-18645-1umkr4m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/94304/original/image-20150909-18645-1umkr4m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/94304/original/image-20150909-18645-1umkr4m.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/94304/original/image-20150909-18645-1umkr4m.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/94304/original/image-20150909-18645-1umkr4m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/94304/original/image-20150909-18645-1umkr4m.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/94304/original/image-20150909-18645-1umkr4m.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Conjunctions between the BARREL balloons and satellites. The green lines marked ‘B-field’ show magnetic field lines.</span>
<span class="attribution"><span class="source">Alexa Halford</span></span>
</figcaption>
</figure>
<h2>Using our data to fill in what we know</h2>
<p>There’s still a lot to do once we wrap up the campaign and head home with our new data – the measurements taken in the magnetosphere during what are essentially space hurricanes. It takes plenty of ingenuity to translate the raw data into scientific understanding, and we have to do a lot of processing and analyzing.</p>
<p>Our “lost” electrons interact with neutral particles in the atmosphere, producing the X-rays our balloons measure. The X-rays let us infer the energy of electrons we’re interested in. We combine our BARREL observations with those of satellites and other ground-based instruments to sort out how much energy the “lost” electrons had before they were lost. No single data set gives us the full picture, so we have to collaborate, fitting each piece of the puzzle together.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/iueTbgU5-NE?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">The size and number of particles in the radiation belts can change drastically over short periods of time.</span></figcaption>
</figure>
<p>Knowing how much energy the electron had before it got lost to the atmosphere, how large a region this phenomenon occurs over and how frequently this occurs gives us a better understanding of how the radiation belts work.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/94311/original/image-20150909-18649-1yzs2o4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/94311/original/image-20150909-18649-1yzs2o4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/94311/original/image-20150909-18649-1yzs2o4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/94311/original/image-20150909-18649-1yzs2o4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/94311/original/image-20150909-18649-1yzs2o4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/94311/original/image-20150909-18649-1yzs2o4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/94311/original/image-20150909-18649-1yzs2o4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/94311/original/image-20150909-18649-1yzs2o4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Sometimes science is done at a coffee shop, where you can find me writing up the next set of papers from our last campaign.</span>
<span class="attribution"><span class="source">Alexa Halford</span></span>
</figcaption>
</figure>
<p>This fall, we’re starting to write up papers and put together presentations about our research to share with colleagues. We were incredibly lucky with this campaign. Every balloon that we sent up got some amazing data! Here’s hoping we’re one step closer to understanding the dynamics of the Earth’s radiation belts.</p><img src="https://counter.theconversation.com/content/46240/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Alexa Halford receives funding from NASA. She is also a member of the Sierra Club. </span></em></p>Geomagnetic storms can interact with particles near Earth, causing issues for satellites and other tech. Researchers send balloons 20 miles into the sky to figure out just what’s going on up there.Alexa Halford, Postdoctoral Research Associate in Physics and Astronomy, Dartmouth CollegeLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/466362015-08-28T13:30:17Z2015-08-28T13:30:17ZSix amazing sights that look even better from the International Space Station<figure><img src="https://images.theconversation.com/files/92927/original/image-20150825-15875-1pkpm9z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Hurricane Arthur photographed by ESA astronaut Alexander Gerst.</span> <span class="attribution"><span class="source">ESA/NASA</span></span></figcaption></figure><p>Imagine seeing the lights of cities spreading around <a href="http://www.nasa.gov/multimedia/imagegallery/image_feature_1923.html">the Nile Delta</a> and then in less than an hour gazing down on <a href="http://www.nasa.gov/multimedia/imagegallery/image_feature_152.html">Mount Everest</a>. The astronauts on the <a href="http://www.nasa.gov/mission_pages/station/main/index.html">International Space Station</a> (ISS) are among the lucky few who will have this humbling, once-in-a-lifetime experience of seeing the beauty of Earth from space. </p>
<p>The ISS doesn’t just offer spectacular and countless views of the natural and man-made landscapes of our planet. It also immerses its residents into the Earth’s space environment and reveals how dynamic its atmosphere is, from its lower layers to its protective <a href="http://www.swpc.noaa.gov/phenomena/earths-magnetosphere">magnetic shield</a>, constantly swept by the solar wind.</p>
<p>The best views are seen from <a href="http://www.esa.int/Our_Activities/Human_Spaceflight/Views_from_Cupola">the Cupola</a>, an observation deck module attached to the ISS in 2010 and comprising seven windows. So, what are the amazing sights that you can see from the space station?</p>
<h2>1. Storms and lightning</h2>
<p>When the ISS orbits over a sea of thunderclouds, it’s not rare for astronauts to witness an impressive amount of lightning. What is unusual, however, is seeing lightning sprites, which were <a href="http://earthobservatory.nasa.gov/IOTD/view.php?id=86463">observed on August 10th</a> by astronauts aboard the space station.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/92911/original/image-20150825-17055-o3talf.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/92911/original/image-20150825-17055-o3talf.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/92911/original/image-20150825-17055-o3talf.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/92911/original/image-20150825-17055-o3talf.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/92911/original/image-20150825-17055-o3talf.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/92911/original/image-20150825-17055-o3talf.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/92911/original/image-20150825-17055-o3talf.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">ISS astronauts spotted a sprite (the red jellyfish-like structure on the right of the image) appearing above thunder clouds on August 10, 2015.</span>
<span class="attribution"><span class="source">NASA</span></span>
</figcaption>
</figure>
<p>Sprites are electrical discharges, similar to thunder lights. However, instead of occurring in the lower layer of Earth’s atmosphere, these very fast, red-coloured discharges (due to the excited nitrogen at this altitude) occur much higher up and are as such difficult to observe from the ground.</p>
<h2>2. Sunrises and sunsets</h2>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/92928/original/image-20150825-15896-1ar0fkw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/92928/original/image-20150825-15896-1ar0fkw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=398&fit=crop&dpr=1 600w, https://images.theconversation.com/files/92928/original/image-20150825-15896-1ar0fkw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=398&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/92928/original/image-20150825-15896-1ar0fkw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=398&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/92928/original/image-20150825-15896-1ar0fkw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/92928/original/image-20150825-15896-1ar0fkw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/92928/original/image-20150825-15896-1ar0fkw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=501&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Sunset over the Indian Ocean.</span>
<span class="attribution"><span class="source">NASA/ESA/G Bacon</span></span>
</figcaption>
</figure>
<p>With the ISS orbiting the Earth every 90 minutes, astronauts can see the Sun rise and set around 16 times every 24 hours. The dramatic views from the station display a rainbow-like horizon as the Sun appears and disappears beyond the horizon.</p>
<p>The changes in colour are due to the angle of the solar rays and their scattering in the Earth’s atmosphere. If similar jaw-dropping views can be seen from Earth, seeing our mother planet lit up in the rising Sun certainly adds to the intensity of the picture.</p>
<h2>3. Stars and the Milky Way</h2>
<figure>
<iframe src="https://player.vimeo.com/video/38409143" width="500" height="281" frameborder="0" webkitallowfullscreen="" mozallowfullscreen="" allowfullscreen=""></iframe>
<figcaption><span class="caption">Amazing sightings of distant astronomical objects as seen from the space shuttle.</span></figcaption>
</figure>
<p>From the ground, atmospheric conditions and light pollution affect our ability to see stars and other celestial bodies. As light travels through layers of hot and cold air, the bending of its rays render a flickering image of these distant objects, while atmospheric particles such as dust prevent from seeing fainter objects such as nebulae and galaxies.</p>
<p>The lack of an atmosphere at the orbiting altitude of the ISS allows the residents on the space station to see the stars, the Milky Way and other astronomical features with much greater clarity than is possible on Earth.</p>
<h2>4. Meteor showers</h2>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/92916/original/image-20150825-17096-duu601.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/92916/original/image-20150825-17096-duu601.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/92916/original/image-20150825-17096-duu601.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/92916/original/image-20150825-17096-duu601.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/92916/original/image-20150825-17096-duu601.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/92916/original/image-20150825-17096-duu601.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/92916/original/image-20150825-17096-duu601.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The disintegration of a Perseid meteor photographed in August 2011 from the ISS.</span>
<span class="attribution"><span class="source">NASA</span></span>
</figcaption>
</figure>
<p>Astronauts aboard the ISS can also witness the disintegration of meteoroids in the Earth’s atmosphere. Those small bodies are fragments detached from celestial bodies such as asteroids and comets. As they enter in the Earth’s atmosphere at great speed, the heat due to the body interaction with air rapidly destroys them. Whereas the chance of seeing them from the ground is very much weather dependent, being on the ISS guarantees the best seats to watch these shooting stars flaming across our planet’s sky.</p>
<h2>5. Auroras</h2>
<p>Also known as northern and southern lights, auroras are created when solar storms, consisting of large magnetised clouds of energetic particles launched from the sun, or strong <a href="http://www.swpc.noaa.gov/phenomena/solar-wind">solar wind</a>, interact with the Earth’s magnetic shield. Upon collision with the Earth, these solar streams energise particles within the planet’s magnetic shield.</p>
<figure>
<iframe src="https://player.vimeo.com/video/130263115" width="500" height="281" frameborder="0" webkitallowfullscreen="" mozallowfullscreen="" allowfullscreen=""></iframe>
<figcaption><span class="caption">Time lapses showing the ISS travelling through auroras.</span></figcaption>
</figure>
<p>When they enter the upper layer of the Earth’s atmosphere, these energetic particles excite nitrogen and oxygen atoms present at these altitudes. Then when they return from their excited state, these atoms emit light of different colours indicative of the amount of energy they absorbed. This typically produces green and red, ribbon-like curtains. </p>
<h2>6. Cosmic rays</h2>
<p><a href="http://helios.gsfc.nasa.gov/gcr.html">Galactic cosmic rays</a> aren’t really a phenomenon you can see. These energetic sub-atomic particles come from intense astronomical sources such as exploding stars or black holes. If they pass into the body they can damage tissue and break DNA, causing various diseases over the course of time.</p>
<p>Most cosmic rays do not penetrate in the thick atmosphere of the Earth. Since the ISS sits outside this protected zone, its astronauts are much more likely to be struck by the particles. Astronauts regularly see <a href="http://www.sciencedirect.com/science/article/pii/S0042698905006735">flashes of light</a> when they close their eyes, which is thought to be caused by cosmic rays interacting with body parts that play role in vision, such as the optic nerve or visual centres in the brain.</p>
<p>Solar storms, which have a strong magnetic structure, act as a shield against cosmic rays. A solar storm passing by the Earth can be indirectly witnessed by astronauts aboard the ISS via a drop in the count of cosmic rays, also known as the “<a href="http://science.nasa.gov/science-news/science-at-nasa/2005/07oct_afraid/">Forbush decrease</a>”. What a sensation it must be to “feel” a storm passing by the Earth’s system.</p><img src="https://counter.theconversation.com/content/46636/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Miho Janvier does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Astronauts living on the ISS get to experience the wonders of the universe’s natural phenomena like no one else.Miho Janvier, Lecturer in Mathematics, University of DundeeLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/450732015-08-17T09:43:01Z2015-08-17T09:43:01ZDamaging electric currents in space affect Earth’s equatorial region, not just the poles<figure><img src="https://images.theconversation.com/files/91512/original/image-20150811-32001-h7ezzh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">When the sun flares, space weather is on its way to Earth.</span> <span class="attribution"><a class="source" href="http://www.nasa.gov/image-feature/solar-dynamics-observatory-sees-m79-class-solar-flare">NASA/SDO</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>The Earth’s magnetic field – known as the “magnetosphere” – protects our atmosphere from the “solar wind.” That’s the constant stream of charged particles flowing outward from the sun. When the magnetosphere shields Earth from these solar particles, they get funneled toward the polar regions of our atmosphere. </p>
<p>As the particles crash into the atmosphere’s ionospheric layer, light is given off, creating beautiful multicolored displays of <a href="https://theconversation.com/what-caused-those-spectacular-northern-lights-and-how-you-can-catch-them-next-time-39081">aurora</a> near both the North and South Poles. These are stunning visual representations of the complex interactions in the near-Earth space environment, which we collectively term “space weather.” </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/91511/original/image-20150811-11104-pjxls4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/91511/original/image-20150811-11104-pjxls4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/91511/original/image-20150811-11104-pjxls4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=401&fit=crop&dpr=1 600w, https://images.theconversation.com/files/91511/original/image-20150811-11104-pjxls4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=401&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/91511/original/image-20150811-11104-pjxls4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=401&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/91511/original/image-20150811-11104-pjxls4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=504&fit=crop&dpr=1 754w, https://images.theconversation.com/files/91511/original/image-20150811-11104-pjxls4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=504&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/91511/original/image-20150811-11104-pjxls4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=504&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Aurora over Norway, visual of space weather.</span>
<span class="attribution"><span class="source">Alexa Halford</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>The same space weather that generates these beautiful displays can cause havoc for a wide range of <a href="https://theconversation.com/divert-power-to-shields-the-solar-maximum-is-coming-11228">technologies</a>. We’ve known for a while that space weather in high-latitude regions near the poles can cause power grid failures, sometimes causing heavy damage. <a href="http://doi.org/10.1029/89EO00409">The most famous</a> instance was the March 1989 blackout in the Northeastern US and up through Quebec, Canada that left millions without power for 12 hours.</p>
<p>But we haven’t thought of equatorial regions as being prime targets. Our new research shows that areas closer to the equator still experience bad space weather – and its disturbing effects on power grid infrastructure.</p>
<h2>Changing magnetic fields crank up electric currents</h2>
<p>High above the ground in the upper atmosphere are fluctuating electric currents driven by interactions in the <a href="http://www.swpc.noaa.gov/phenomena/earths-magnetosphere">magnetosphere</a> and <a href="http://www.ips.gov.au/Educational/1/2/5">ionosphere</a>. These atmospheric currents cause strong changes in the strength of the local magnetic field on the ground. We can’t feel the magnetic field ourselves, but researchers <a href="http://www.intermagnet.org/">measure and track it</a> at various points on the Earth’s surface. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/91505/original/image-20150811-11104-1ptmk6c.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/91505/original/image-20150811-11104-1ptmk6c.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/91505/original/image-20150811-11104-1ptmk6c.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/91505/original/image-20150811-11104-1ptmk6c.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/91505/original/image-20150811-11104-1ptmk6c.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/91505/original/image-20150811-11104-1ptmk6c.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/91505/original/image-20150811-11104-1ptmk6c.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/91505/original/image-20150811-11104-1ptmk6c.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Dr Endawoke Yizengaw next to a magnetometer installation that records changes in the magnetic field at that spot in Phuket, Thailand.</span>
<span class="attribution"><span class="source">Endawoke Yizengaw</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>That’s all well and good. The problem comes in when these atmospheric currents cause swift changes in the magnetic field. When the magnetic field abruptly changes, it can generate electric currents in conductors at the Earth’s surface – for instance, long pipes or wires such as <a href="https://www.lloyds.com/%7E/media/lloyds/reports/360/360%20space%20weather/7311_lloyds_360_space%20weather_03.pdf">oil and gas pipelines</a> or <a href="https://eos.org/features/magnetic-storms-induction-hazards">power transmission lines</a>. This process of electric current generation is called <a href="https://www.youtube.com/watch?v=S0wbEl7caTY">magnetic induction</a>.</p>
<p>These electric currents are not-so-creatively called geomagnetically induced currents, or GICs for short. The high-latitude regions are most susceptible to GICs because of the intense electric currents flowing through the auroras, thanks to the way the solar wind gets diverted when it hits the Earth’s magnetosphere. However, the entire planet can be affected to varying degrees.</p>
<p>When they occur, GICs effectively generate extra electric current in power grid infrastructure through magnetic induction. Power grids, during large events, can end up taking on more electricity than they can handle. These induced currents have caused numerous <a href="http://aurora.fmi.fi/gic_service/english/about_ground_effects.html">equipment failures</a> that have led to power outages for large populations.</p>
<figure><img src="https://cdn.theconversation.com/static_files/files/28/animate6.gif?1518674322"><figcaption><span class="caption">Modeled location of the equatorial electrojet from the viewpoint of a satellite sitting at about 10:00 am local time (Alken and Maus, 2007).</span></figcaption></figure>
<h2>Trouble at the equator too, not just near the poles</h2>
<p>Those same geomagnetically induced currents that happen in the high-latitude regions can happen around the equator of our planet too. There, they are caused not by the auroral electric current system we find near the poles, but by a weaker low-latitude counterpart called the <a href="http://geomag.org/info/equatorial_electrojet.html">equatorial electrojet</a>. Like the high-latitude ionospheric current system, the equatorial electrojet’s electric current can be detected on the ground using magnetic field observations.</p>
<p>Recently researchers <a href="http://dx.doi.org/10.1029/2011SW000750">reported</a> that GIC activity is enhanced at the equator during severe geomagnetic storms – that’s when solar eruptions called “<a href="http://www.space.com/11506-space-weather-sunspots-solar-flares-coronal-mass-ejections.html">coronal mass ejections</a>” trigger shock waves that hit the Earth. They pointed the finger at the equatorial electrojet as a suspected cause.</p>
<p>In our new research article in <a href="http://doi.org/10.1002/2015GL065060">Geophysical Research Letters</a>, we show that countries near the <a href="http://www.bu.edu/cism/cismdx/ref/Labs/2005_AFWA_ShortCourse/Lab03/refs/EarthMagneticField.pdf">magnetic equator</a> are more vulnerable to space weather than previously thought.</p>
<p>Rather than focusing on <a href="https://theconversation.com/solar-eruption-could-help-earth-prepare-for-technology-melt-down-18747">severe geomagnetic storms</a>, such as the <a href="http://www.space.com/23396-scary-halloween-solar-storm-2003-anniversary.html">2003 Halloween event</a> that caused power grid problems in Sweden (among many <a href="http://www.nws.noaa.gov/os/assessments/pdfs/SWstorms_assessment.pdf">other things</a>), we took a different tack. Our analysis focused on the arrival of interplanetary shocks. These are abrupt pressure increases in the solar wind - that stream of plasma constantly flowing out of the sun. When these shocks hit the Earth’s magnetosphere, the impact causes a sudden magnetic field change that can be measured all over the world.</p>
<p>Interplanetary shocks regularly announce the beginning of a geomagnetic storm. But many pass by relatively benignly without developing into a full-blown geomagnetic storm. We noticed that the magnetic response to these shock arrivals was sometimes significantly stronger at the magnetic equator when compared to locations only a few degrees away. Why?</p>
<p>An analysis of how these equatorial responses differed throughout the day revealed they were strongest around noon and weakest at night. This daily contrast corresponds to the well-known variations in the equatorial electrojet. It’s strong evidence that the equatorial electrojet is amplifying the geomagnetically induced current activity during interplanetary shock arrivals in a way that hasn’t really been recognized until now.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/91510/original/image-20150811-11091-1wtqiwj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/91510/original/image-20150811-11091-1wtqiwj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/91510/original/image-20150811-11091-1wtqiwj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/91510/original/image-20150811-11091-1wtqiwj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/91510/original/image-20150811-11091-1wtqiwj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/91510/original/image-20150811-11091-1wtqiwj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=425&fit=crop&dpr=1 754w, https://images.theconversation.com/files/91510/original/image-20150811-11091-1wtqiwj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=425&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/91510/original/image-20150811-11091-1wtqiwj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=425&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Nonpolar power grids can get hit by space weather, too.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/kendoerr/8079981829">Ken Doerr</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<h2>Effects on equatorial power grids</h2>
<p>This result has significant implications for the many countries located beneath the equatorial electrojet that may be operating power infrastructure not initially designed to cope with space weather. These countries need to look into ways of protecting their infrastructure during geomagnetically quiet periods as well as during severe geomagnetic storms.</p>
<p>One of our coauthors, Dr <a href="https://www2.bc.edu/endawoke-kassie/">Endawoke Yizengaw</a> from Boston College, grew up in Ethiopia, within the equatorial electrojet’s region of influence. He recalls regular unexplained power outages during his childhood and wonders whether interplanetary shocks may have played a role. We hope to be able to answer this question in the near future.</p>
<p>Scientists around the world are conducting ongoing research to better understand the effects of these geomagnetically induced currents on power grids. It’s becoming increasingly clear that we need to investigate the effects of quiet periods, not just major events. What happens during these quiet times, and in regions often overlooked, can have a significant impact on our increasingly technology-dependent society.</p><img src="https://counter.theconversation.com/content/45073/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Brett Carter receives funding from the Victorian Government Department of Business and Innovation and the Australian Research Council.</span></em></p><p class="fine-print"><em><span>Alexa Halford receives funding from NASA through multiple grants, primarily NNX08AM58G (BARREL). Alexa is also a member of the Sierra Club.</span></em></p>Our power grid infrastructure on Earth is more vulnerable to space weather than previously thought – with susceptibility in more regions and even during quiet geomagnetic periods.Brett Carter, Senior Research Fellow, RMIT UniversityAlexa Halford, Researcher in Physics and Astronomy, Dartmouth CollegeLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/391132015-04-01T19:09:55Z2015-04-01T19:09:55ZFire in the sky: The southern lights in Indigenous oral traditions<figure><img src="https://images.theconversation.com/files/76189/original/image-20150326-8716-7y646s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Aurora Australis as seen from Victoria.</span> <span class="attribution"><a class="source" href="http://www.terrastro.com/galleries/red-aurora/">Alex Cherney, Terrastro Gallery</a>, <span class="license">Author provided</span></span></figcaption></figure><p>Parts of Australia have been privileged to see dazzling lights in the night sky as the Aurora Australis – known as the southern lights – <a href="https://theconversation.com/dazzled-by-the-bright-southern-lights-39129">puts on a show</a> this year.</p>
<p>A recent surge in solar activity caused spectacular auroral displays across the world. While common over the polar regions, aurorae are rare over Australia and are typically restricted to far southern regions, such as Tasmania and Victoria.</p>
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<p>But recently, aurorae have been visible over the whole southern half of Australia, seen as far north as Uluru and Brisbane.</p>
<h2>Different cultures</h2>
<p>It’s a phenomenon that has existed since the Earth’s formation and has been witnessed by cultures around the world. These cultures developed their own explanation for the lights in the sky – many of which are strikingly similar.</p>
<p>From a scientific point of view, aurora form when charged particles of solar wind are channelled to the polar regions by Earth’s magnetic field. These particles ionize oxygen and nitrogen molecules in the upper atmosphere, creating light.</p>
<p>Auroral displays can show various colours, from white, to yellow, red, green, and blue. They can appear as a nebulous glowing arcs or curtains waving across the sky.</p>
<p>Aurorae are also reported to make <a href="http://www.space.com/16498-northern-lights-clapping-sound-explained.html">strange sounds</a> on rare occasions. Witnesses describe it as a crackling sound, like rustling grass or radio static.</p>
<p>In the Arctic, the <a href="http://www.damninteresting.com/the-sound-of-the-aurora/">Inuit</a> say the noise is made by spirits playing a game or trying to communicate with the living.</p>
<p>In 1851, Aboriginal people near Hobart said an aurora made noise like “people snapping their fingers”. The cause of this noise is unknown.</p>
<figure>
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</figure>
<p>Aurorae are significant in <a href="https://theconversation.com/stories-from-the-sky-astronomy-in-indigenous-knowledge-33140">Australian Indigenous astronomical traditions</a>. Aboriginal people associate aurorae with fire, death, blood, and omens, sharing many similarities with <a href="http://www.ewebtribe.com/NACulture/articles/aurora.html">Native American</a> communities. They are quite different from Inuit traditions of the Aurora Borealis, which are more festive.</p>
<h2>Fire in the sky</h2>
<p>Aboriginal people commonly saw aurorae as fires in the cosmos. To the Gunditjmara of western Victoria, they’re Puae buae (“ashes”). To the Gunai of eastern Victoria, they’re bushfires in the spirit world and an omen of a coming catastrophe.</p>
<p>The Dieri and Ngarrindjeri of South Australia see aurora as fires created by sky spirits.</p>
<p>As far north as southwestern Queensland, Aboriginal people saw the phenomenon as “feast fires” of the Oola Pikka —- ghostly beings who spoke to Elders through the aurora.</p>
<p>The Maori of Aotearoa/New Zealand saw aurorae (Tahunui-a-rangi) as the campfires of ancestors reflected in the sky. These ancestors sailed southward in their canoes and settled on a land of ice in the far south.</p>
<p>The southern lights let people know they will one day return. This is similar to an <a href="http://www.indigenouspeople.net/aurora.htm">Algonquin story</a> from North America. </p>
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<h2>A warning to follow sacred law</h2>
<p>Mungan Ngour, a powerful sky ancestor in Gunai traditions, set rules for male initiation and put his son, Tundun, in charge of the ceremonies. When people leaked secret information about these ceremonies, Mungan cast down a great fire to destroy the Earth. The people saw this as an aurora.</p>
<p>Near Uluru, a group of hunters broke Pitjantjatjara law by killing and cooking a sacred emu. They saw smoke rise to the south, towards the land of Tjura. This was the aurora, viewed as poisonous flames that signalled coming punishment.</p>
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<p>The Dieri also believe an aurora is a warning that someone is being punished for breaking traditional laws, which causes great fear. The breaking of traditional laws would result in an armed party coming to kill the lawbreakers when they least expect it.</p>
<p>In this context, fear of an aurora was utilised to control behaviour and social standards.</p>
<h2>Blood in the cosmos</h2>
<p>The red hue of some aurorae is commonly associated with blood and death.</p>
<p>To Aboriginal communities across New South Wales, Victoria, and South Australia, auroral displays represented blood that was shed by warriors fighting a great battle in the sky, or by spirits of the dead rising to the heavens.</p>
<p>Celestial events that appear red are often linked to blood, including <a href="http://www.abc.net.au/science/articles/2011/03/15/3160848.htm">meteors</a> and <a href="http://www.abc.net.au/science/articles/2011/06/15/3244593.htm">eclipses</a>.</p>
<p>A total lunar eclipse turns the moon red (sometimes called a blood-moon), which was seen by some communities as the spirit of a dead man rising from his grave.</p>
<p>Rare astronomical events were viewed as bad omens by cultures around the world. Now imagine if two of these events overlap!</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/75481/original/image-20150320-5749-55uma.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/75481/original/image-20150320-5749-55uma.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/75481/original/image-20150320-5749-55uma.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=397&fit=crop&dpr=1 600w, https://images.theconversation.com/files/75481/original/image-20150320-5749-55uma.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=397&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/75481/original/image-20150320-5749-55uma.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=397&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/75481/original/image-20150320-5749-55uma.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=499&fit=crop&dpr=1 754w, https://images.theconversation.com/files/75481/original/image-20150320-5749-55uma.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=499&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/75481/original/image-20150320-5749-55uma.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=499&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The moon turning red during an eclipse, also known as a blood moon.</span>
<span class="attribution"><span class="source">NASA</span></span>
</figcaption>
</figure>
<p>In 1859, Aboriginal people in South Australia witnessed an auroral display <em>and</em> a total lunar eclipse. This caused great fear an anxiety, signalling the arrival of dangerous spirit beings.</p>
<p>There could be a repeat of this astronomical double-act as <a href="https://theconversation.com/be-prepared-for-the-shortest-total-lunar-eclipse-of-the-century-39575">a lunar eclipse</a> will be <a href="http://www.timeanddate.com/eclipse/lunar/2015-april-4">visible across Australia</a> on Saturday April 4, 2015.</p>
<p>Will the aurorae continue? Keep watch.</p>
<hr>
<p>See also: <a href="https://theconversation.com/be-prepared-for-the-shortest-total-lunar-eclipse-of-the-century-39575">Be prepared for the shortest total lunar eclipse of the century</a></p><img src="https://counter.theconversation.com/content/39113/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Duane Hamacher receives funding from the Australian Research Council.</span></em></p>The southern lights that put on a show recently across parts of Australia are easily explained by science. But some cultures have their own explanation for these dazzling lights in the sky.Duane Hamacher, Lecturer and ARC Discovery Early Career Research Fellow, UNSW SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/390812015-03-19T17:57:21Z2015-03-19T17:57:21ZWhat caused those spectacular northern lights – and how you can catch them next time<p>Catching a glimpse of the northern lights is apparently the <a href="http://www.mirror.co.uk/news/uk-news/holiday-bucket-list-northern-lights-2866993">top experience</a> for Britons compiling a “bucket list” of must-do experiences before they die. It’s not surprising, the aurora borealis is a breathtakingly beautiful natural phenomenon, but one that is seldom seen from the British Isles.</p>
<p>Nevertheless, on the morning of March 18, the British press were reporting a <a href="http://www.bbc.co.uk/news/uk-31936513">brilliant display</a> of the northern lights the previous night. Social media was <a href="http://www.huffingtonpost.co.uk/2015/03/18/aurora-borealis-uk-pictures-north-of-england_n_6891724.html">overflowing</a> with photographic evidence of a display stretching from Scotland to Somerset. But what had brought the lights to the UK that night?</p>
<p>The story begins in the early hours of March 15, when a magnetically active region of the Sun’s surface crackled and erupted, hurling billions of tonnes of the solar atmosphere out into the solar system. Unless you have a keen interest in our local star, you were probably unaware this had happened. It didn’t make the news. But for scientists studying how solar activity affects the space environment surrounding our planet, it was the start of an interesting couple of days.</p>
<figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/75412/original/image-20150319-1562-dhmusn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/75412/original/image-20150319-1562-dhmusn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=606&fit=crop&dpr=1 600w, https://images.theconversation.com/files/75412/original/image-20150319-1562-dhmusn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=606&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/75412/original/image-20150319-1562-dhmusn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=606&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/75412/original/image-20150319-1562-dhmusn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=762&fit=crop&dpr=1 754w, https://images.theconversation.com/files/75412/original/image-20150319-1562-dhmusn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=762&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/75412/original/image-20150319-1562-dhmusn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=762&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Next stop: planet Earth.</span>
<span class="attribution"><a class="source" href="http://www.nasa.gov/mission_pages/sunearth/news/News060711-blast.html#.VQsDsinA7bg">NASA</a></span>
</figcaption>
</figure>
<p>Within hours, the trajectory of this magnetised outpouring of subatomic particles had been modelled. The cloud, known as a coronal mass ejection (CME), was heading in our direction at about one million miles an hour. It looked like it would deliver a glancing blow to planet Earth some time on March 17, but what would happen if it did? Space weather forecasters the world over set to work.</p>
<p>A likely outcome in this scenario is that the arrival of the CME will trigger a geomagnetic storm. This occurs when the magnetic field within the CME couples with the Earth’s magnetic field, allowing energy and matter to transfer from the CME to the near-Earth space environment. </p>
<p>The most obvious symptom of a geomagnetic storm is more intense aurora borealis due to the increased inflow of electrically-charged particles to the Earth’s upper atmosphere. But <a href="https://theconversation.com/electromagnetic-disaster-could-cost-trillions-and-affect-millions-we-need-to-be-prepared-30296">less attractive side-effects</a> include disruption to hi-tech navigation and communications systems, and the risk of damage to satellites and power grids. Space weather forecasting, while still in its infancy, is a <a href="https://theconversation.com/why-were-preparing-weather-forecasts-in-space-32638">serious business</a>.</p>
<p>By March 16, forecasters at the US <a href="http://www.swpc.noaa.gov/">Space Weather Prediction Center</a> were predicting the CME would <a href="http://www.swpc.noaa.gov/news/g1-minor-geomagnetic-storm-watch-18-march">trigger a geomagnetic storm</a> in the days that followed. Then, at around 4am UK time on March 17, it engulfed NASA’s Advanced Composition Explorer (ACE) satellite, the space weather monitor that constantly samples the solar wind upstream of the Earth. </p>
<p>For the first time since it left the Sun, it was possible to measure the orientation of the magnetic field inside the CME. The orientation of this field, the remnants of the Sun’s magnetic field torn away when the CME was launched, is crucial. It controls the coupling between the CME and the Earth’s own magnetic field. Although it can take almost any orientation, if the field inside the CME points southwards, it will oppose the Earth’s magnetic field (which, as any compass shows, points north) and these opposite polarity fields interact strongly. If the CME’s field points northward, the interaction is much weaker.</p>
<p>The satellite revealed that the field inside the incoming CME was strong, and as it streamed past the Earth over the course of the morning, it fluctuated between northward and southward orientations, triggering mild geomagnetic disturbances. Then around noon, the CME’s magnetic field turned southward and stayed southward for the next 12 hours. The strong and sustained coupling poured energy into the magnetosphere, the region of space normally dominated by the Earth’s magnetic field, triggering the strongest and longest geomagnetic storm of the Sun’s current 11-year cycle of activity.</p>
<p>Excited aurora-spotters all over the globe weren’t disappointed. As night fell, the northern lights, and their southern counterpart the aurora australis, lit the skies with dancing displays of green and red light. Normally concentrated in ring-like ovals that circle our planet’s magnetic poles, the auroral zones expanded equatorward, pushing auroral displays as far south as Kansas and <a href="http://www.insidenova.com/headlines/northern-lights-over-northern-virginia/article_cb1b7aea-cd00-11e4-a578-eb344d9e03d1.html">Virginia</a> in the northern hemisphere, and as far north as <a href="http://www.stuff.co.nz/science/67442162/that-was-an-aurora-australis-of-rare-grandeur">New Zealand</a> and Australia. In the UK, those hoping to see the aurora were battling a blanket of mist and fog that settled across much of the country, but many of those with clear a view of the sky reported sightings of the northern lights.</p>
<p>Although the biggest geomagnetic storm of the current solar cycle, this St. Patrick’s Day storm was not a once-in-a-lifetime space weather event. Mid-latitude aurora sightings are rare, but typically occur a handful of times in each 11-year solar cycle. The current solar maximum is not as intense as the previous peak in 2003 and the frequency and severity of geomagnetic storms has been lower. Over the coming days, high-tech infrastructure operators will look at how their systems responded to the storm, but the early indications are that there were no significant problems.</p>
<h2>Northern likes</h2>
<p>So if this wasn’t a unique event, why did it make the headlines? One reason why public interest in the northern lights has increased since the previous solar cycle is the advent of social media and mobile technology. Now anyone can sign up to space weather alerts and have warnings of solar flares, CME eruptions or geomagnetic activity delivered to the phone in near real-time. Hopeful aurora spotters can find out what others in their country or region are seeing and interact with them easily, most commonly by using the #aurora hashtag.</p>
<p>Lancaster University’s <a href="http://aurorawatch.lancs.ac.uk">AuroraWatchUK</a> service is Britain’s most popular aurora alerting system and uses real-time magnetic field measurements from across the UK to sense the geomagnetic disturbances associated with the northern lights. Social media channels now mean our alerts can reach huge numbers, improving the odds of people seeing the aurora from their back garden. During the St. Patrick’s Day storm, our social media posts reached more than 200,000 people, with thousands of <a href="https://www.facebook.com/aurorawatchuk/posts/859762350748165">shares</a> and <a href="https://twitter.com/aurorawatchuk/status/577935726358167552">retweets</a>.</p>
<p>For UK-based aurora-spotters, geographic location, weather and light pollution are not ideal. But if you want to tip the odds slightly in your favour, as well as looking up, you should really think about looking at your phone.</p><img src="https://counter.theconversation.com/content/39081/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jim Wild receives funding from the Science and Technology Facilities Council and the Natural Environment Research Council. He is also the vice-President (Geophysics) of the Royal Astronomical Society. He occasionally works with a variety of UK-based travel and tourism companies to engage relevant audiences on topics related to his research.</span></em></p>How scientists tracked a massive emission from the sun right across the solar system.Jim Wild, Professor of Space Physics, Lancaster UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/370052015-02-06T06:14:49Z2015-02-06T06:14:49ZRocket into Northern Lights studies the “Invisible Aurora’s” electric currents<figure><img src="https://images.theconversation.com/files/70951/original/image-20150203-25540-1a0n2hg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Time exposed photo of the Auroral Spatial Structures Probe Launch into the aurora.</span> <span class="attribution"><span class="source">Merrick Peirce </span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><p>The aurora borealis lights up the Arctic night skies. Also called the Northern Lights, the phenomenon is the result of beams of charged particles tracing along the Earth’s magnetic field and entering the atmosphere. When they collide with oxygen and nitrogen in the atmosphere, the gases glow green, red and blue depending on the beam energy.</p>
<p>While stunning for observers on the ground, aurora can cause problems for satellites as they orbit the Earth, along with all the technologies that rely on them. The aurora is accompanied by large electric currents that flow invisibly in the upper atmosphere, increasing the temperature around the aurora from about 260F (125C) to 980F (525C). This heating causes the thin upper atmosphere to expand, changing the slight drag on satellites and thereby shifting their orbital motion over time.</p>
<p>This satellite drag is the limiting factor on how far into the future one can predict a satellite’s position. Satellite operators are continually looking for better models of satellite drag so they could plan further into the future and preserve the precious fuel necessary to correct satellite orbits. The key to prediction is an understanding of the energy input during an aurora display.</p>
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<figcaption>
<span class="caption">Aurora over Alaska as seen from the International Space Station.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/nasamarshall/14743794785">NASA</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc/4.0/">CC BY-NC</a></span>
</figcaption>
</figure>
<p>There have been maybe a hundred or so rockets launched into the aurora over the last 50 years to measure its energy flow. But those missions only took single measurements at the points where a rocket passed over the aurora. Our recent Auroral Spatial Structures Probe mission took a whole new approach to try to answer questions about the voltages and current surrounding the aurora and how they change over time.</p>
<h2>Alaskan launch</h2>
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<a href="https://images.theconversation.com/files/71092/original/image-20150204-28605-av3too.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/71092/original/image-20150204-28605-av3too.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/71092/original/image-20150204-28605-av3too.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=402&fit=crop&dpr=1 600w, https://images.theconversation.com/files/71092/original/image-20150204-28605-av3too.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=402&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/71092/original/image-20150204-28605-av3too.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=402&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/71092/original/image-20150204-28605-av3too.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=505&fit=crop&dpr=1 754w, https://images.theconversation.com/files/71092/original/image-20150204-28605-av3too.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=505&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/71092/original/image-20150204-28605-av3too.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=505&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The rocket in its Styrofoam box that protects against extreme cold.</span>
<span class="attribution"><span class="source">Tim Neilsen/Space Dynamics Laboratory</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>The Sun never shines on the launch pads at the Poker Flat Research Range during the winter. Just outside of Fairbanks, Alaska, the range is nestled in a valley surrounded by rolling hills and shadows. It was -44F (-42C) outside and the NASA Auroral Spatial Structures Probe sat on a pad in a large Styrofoam box custom built to surround the 70-foot unmanned rocket. Warm air was blown into the box to keep the rocket – and all its scientific instruments – at room temperature. I sat in an equally warm science operations center at the top of the hill with my colleagues from the University of Alaska staring at computer screens that monitored the aurora borealis, the Earth’s magnetic field and the solar wind. </p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/ldZbPSzx7sk?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
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<p>I picked up the intercom to say “Operations Center, let’s pick up the count. It is time to spend this rocket.” We had all been waiting for the aurora to appear brightly and be located in the right spot for the rocket flight. The countdown continued, ending in the traditional 10, 9, 8…. At zero, the 4-stage Oriole sounding rocket roared to life ripping right through the Styrofoam and up into the sky. There was a body-penetrating roar. Of course I had to run outside to watch as five years of planning and work was launched into the sky at exactly 1:41 a.m. Alaska Time on Wednesday, January 28. Who wouldn’t?</p>
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<a href="https://images.theconversation.com/files/70810/original/image-20150202-8997-b5x01g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/70810/original/image-20150202-8997-b5x01g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/70810/original/image-20150202-8997-b5x01g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=960&fit=crop&dpr=1 600w, https://images.theconversation.com/files/70810/original/image-20150202-8997-b5x01g.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=960&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/70810/original/image-20150202-8997-b5x01g.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=960&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/70810/original/image-20150202-8997-b5x01g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1206&fit=crop&dpr=1 754w, https://images.theconversation.com/files/70810/original/image-20150202-8997-b5x01g.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1206&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/70810/original/image-20150202-8997-b5x01g.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1206&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The NASA Oriole 4 rocket carrying the Auroral Spatial Structures Probe breaking free from the Styrofoam thermal enclosure upon launch.</span>
<span class="attribution"><span class="source">NASA</span></span>
</figcaption>
</figure>
<h2>So what was it probing?</h2>
<p>The “Visible Aurora” is very active, and beautiful. You can see changes that happen in fractions of seconds and within a few minutes, arcs can explode across the whole sky or simply disappear. We think the underling voltages and currents, the “Invisible Aurora,” are equally active but we don’t know. For example, features in the aurora that are 10 to 100 meters in size might last a few second while something that is 1 to 50 km in size might persist much longer, maybe seconds to minutes, but we just don’t know. </p>
<p>If it were physically possible, I would have instruments remain stationary about 200 to 300 km above the Earth and within the aurora to make measurements over time of the currents and voltages driving them. Ideally, I’d like to have a whole bunch of them spread out, just sitting in place and not moving relative to the Earth while taking data, but that’s not possible. We don’t have an anti-gravity device to allow the payloads to hover at some spot over the Earth in space. The next best thing is to have multiple payloads follow the same path. Each payload then makes a measurement at some location in the aurora as it passes by.</p>
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<a href="https://images.theconversation.com/files/71094/original/image-20150204-28594-1owhe73.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/71094/original/image-20150204-28594-1owhe73.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/71094/original/image-20150204-28594-1owhe73.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/71094/original/image-20150204-28594-1owhe73.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/71094/original/image-20150204-28594-1owhe73.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/71094/original/image-20150204-28594-1owhe73.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/71094/original/image-20150204-28594-1owhe73.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/71094/original/image-20150204-28594-1owhe73.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Making repairs just hours before launch when a a transmitter onboard one of the payloads failed.</span>
<span class="attribution"><span class="source">Tim Neilsen/Space Dynamics Laboratory </span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>This is what we have done with the Auroral Spatial Structures Probe mission: we shot away multiple small payloads in precise directions so that we created a formation of sensors that pass through the same locations in space on a staggered time frame. NASA engineers at the Wallops Flight facility built an ejection system based on compressed air to shoot away small payloads at high speed. They get hit with 200 G of acceleration as they are kicked off and travel the length of a football field in two seconds. My group at the Utah State University Space Dynamics Lab built the small payload and science instruments to measure voltages and currents around the aurora and the density of the ionosphere.</p>
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<a href="https://images.theconversation.com/files/70949/original/image-20150203-25531-vm0pg5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/70949/original/image-20150203-25531-vm0pg5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/70949/original/image-20150203-25531-vm0pg5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=800&fit=crop&dpr=1 600w, https://images.theconversation.com/files/70949/original/image-20150203-25531-vm0pg5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=800&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/70949/original/image-20150203-25531-vm0pg5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=800&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/70949/original/image-20150203-25531-vm0pg5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1005&fit=crop&dpr=1 754w, https://images.theconversation.com/files/70949/original/image-20150203-25531-vm0pg5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1005&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/70949/original/image-20150203-25531-vm0pg5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1005&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Three of the instrumented sub-payloads attached to the forward end of the payload.</span>
<span class="attribution"><span class="source">Charles Swenson</span>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span>
</figcaption>
</figure>
<p>Six small payloads were ejected in pairs from each end of the rocket, three on each end. Four were placed in a line with the main payload, making the fifth in that string. The other two were sent out to the sides. It’s the most complex sounding rocket mission NASA has ever done. It was like flying seven sounding rockets at once over the aurora. </p>
<p>The whole mission only lasted about 14 minutes with about eight of those minutes dedicated to science collection. We measured the magnetic fields using sensitive magnetometers from which auroral currents are computed. We also observed the electric fields and ionospheric density at each of the payloads. We had to predict where the aurora would be 10 to 20 minutes from the time we set the launch in motion – and we nailed it. After reaching an altitude of 521 km – about 120 km higher than the International Space Station – the sensors and spent rocket boosters splashed down in the Arctic Ocean north of Alaska. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/71095/original/image-20150204-28621-m6wwvr.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/71095/original/image-20150204-28621-m6wwvr.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/71095/original/image-20150204-28621-m6wwvr.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=134&fit=crop&dpr=1 600w, https://images.theconversation.com/files/71095/original/image-20150204-28621-m6wwvr.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=134&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/71095/original/image-20150204-28621-m6wwvr.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=134&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/71095/original/image-20150204-28621-m6wwvr.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=168&fit=crop&dpr=1 754w, https://images.theconversation.com/files/71095/original/image-20150204-28621-m6wwvr.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=168&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/71095/original/image-20150204-28621-m6wwvr.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=168&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">NASA engineers work inside the telemetry station where data from the rocket’s payloads are collected and analyzed.</span>
<span class="attribution"><span class="source">Tim Neilsen/Space Dynamics Laboratory</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>We have good data from all of the instruments and now we begin the detailed analysis. Understanding the size of the regions where the energy is input and how much the energy varies with time will calibrate satellite drag models. With luck what we learn from this mission will help satellite operators plan further into the future.</p><img src="https://counter.theconversation.com/content/37005/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Charles Swenson receives funding from NASA and the NSF to study space weather.</span></em></p>The aurora borealis lights up the Arctic night skies. Also called the Northern Lights, the phenomenon is the result of beams of charged particles tracing along the Earth’s magnetic field and entering the…Charles Swenson, Professor of Electrical and Computer Engineering, Utah State UniversityLicensed as Creative Commons – attribution, no derivatives.