tag:theconversation.com,2011:/au/topics/aurorae-38035/articlesAurorae – The Conversation2019-05-20T10:18:45Ztag:theconversation.com,2011:article/1172372019-05-20T10:18:45Z2019-05-20T10:18:45ZThe Earth’s magnetic north pole is shifting rapidly – so what will happen to the northern lights?<figure><img src="https://images.theconversation.com/files/275022/original/file-20190516-69204-7vunsn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Northern lights in Lake Lappajärvi, Finland.</span> <span class="attribution"><span class="source">Santeri Viinamäki</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>Like most planets in our solar system, the Earth has its own magnetic field. Thanks to its <a href="https://theconversation.com/curious-kids-what-would-happen-if-the-earths-core-went-cold-107537">largely molten iron core</a>, our planet is in fact a bit like a bar magnet. It has a north and south magnetic pole, separate from the geographic poles, with a field connecting the two. This field protects our planet from radiation and is responsible for creating the northern and southern lights – spectacular events that are only visible near the magnetic poles.</p>
<p>However, with reports that the magnetic north pole has started moving swiftly at 50km per year – and may soon be over Siberia – it has long been unclear whether the northern lights will move too. Now a new study, <a href="https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2019GL082159">published in Geophysical Research Letters</a>, has come up with an answer. </p>
<p>Our planetary magnetic field has many advantages. For over 2,000 years, travellers <a href="http://www.historyofcompass.com/compass-history/invention-of-the-compass/">have been able to use</a> it to navigate across the globe. <a href="https://theconversation.com/migrating-birds-use-a-magnetic-map-to-travel-long-distances-82624">Some animals</a> even seem to be able to find their way thanks to the magnetic field. But, more importantly than that, our geomagnetic field helps <a href="https://theconversation.com/how-did-mars-lose-its-habitable-climate-the-answer-is-blowing-in-the-solar-wind-50258">protect all life on Earth</a>. </p>
<p>Earth’s magnetic field extends hundreds of thousands of kilometres out from the centre of our planet – stretching right out into interplanetary space, forming what scientists call a “<a href="https://theconversation.com/weve-discovered-the-worlds-largest-drum-and-its-in-space-111465">magnetosphere</a>”. This magnetosphere helps to deflect solar radiation and cosmic rays, preventing the destruction of our atmosphere. This protective magnetic bubble isn’t perfect though, and some solar matter and energy can transfer into our magnetosphere. As it is then funnelled into the poles by the field, it results in the spectacular displays of the <a href="https://theconversation.com/what-caused-those-spectacular-northern-lights-and-how-you-can-catch-them-next-time-39081">northern lights</a>. </p>
<h2>A wandering pole</h2>
<p>Since Earth’s magnetic field is created by its moving, molten iron core, its poles aren’t stationary and they wander independently of one another. In fact, since its first formal discovery in 1831, the north magnetic pole has travelled over 2,000km from the Boothia Peninsula in the far north of Canada to high in the Arctic Sea. This wandering has generally been quite slow, around 9km a year, allowing scientists to easily keep track of its position. But since the turn of the century, this speed has increased to <a href="https://www.nature.com/articles/d41586-019-00007-1">50km a year</a>. The south magnetic pole is also moving, though at a much slower rate (10-15km a year).</p>
<p>This rapid wandering of the north magnetic pole has caused some problems for scientists and navigators alike. Computer models of where the north magnetic pole might be in the future have become seriously outdated, making accurate compass-based navigation difficult. Although GPS does work, it can <a href="https://mycoordinates.org/challenges-for-positioning-and-navigation-in-the-arctic/">sometimes be unreliable</a> in the polar regions. In fact, the pole is moving so quickly that scientists responsible for mapping the Earth’s magnetic field were recently <a href="https://www.ncei.noaa.gov/news/world-magnetic-model-out-cycle-release">forced to update</a> their model much earlier than expected.</p>
<h2>Will the aurora move?</h2>
<p>The <a href="https://theconversation.com/what-caused-those-spectacular-northern-lights-and-how-you-can-catch-them-next-time-39081">aurora</a> generally form in an oval about the magnetic poles, and so if those poles move, it stands to reason that the aurora might too. With predictions suggesting that the north pole will soon be approaching northern Siberia, what effect might that have on the aurora?</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>The northern lights are currently mostly visible from northern Europe, Canada and the northern US. If, however, they shifted north, across the geographic pole, following the north magnetic pole, then that could well change. Instead, the northern lights would become more visible from Siberia and northern Russia and less visible from the much more densely populated US/Canadian border.</p>
<p>Fortunately, for those aurora hunters in the northern hemisphere, it seems as though this might not actually be the case. <a href="https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2019GL082159">A recent study</a> made a computer model of the aurora and the Earth’s magnetic poles based on data dating back to 1965. It showed that rather than following the magnetic poles, the aurora follows the “<a href="http://wdc.kugi.kyoto-u.ac.jp/poles/polesexp.html">geomagnetic poles</a>” instead. There’s only a small difference between these two types of poles –- but it’s an important one. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/275021/original/file-20190516-69189-feozze.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/275021/original/file-20190516-69189-feozze.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=605&fit=crop&dpr=1 600w, https://images.theconversation.com/files/275021/original/file-20190516-69189-feozze.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=605&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/275021/original/file-20190516-69189-feozze.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=605&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/275021/original/file-20190516-69189-feozze.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=761&fit=crop&dpr=1 754w, https://images.theconversation.com/files/275021/original/file-20190516-69189-feozze.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=761&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/275021/original/file-20190516-69189-feozze.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=761&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">Magnetic versus geomagnetic poles.</span>
<span class="attribution"><span class="source">wikipedia.</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
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<p>The magnetic poles are the points on the Earth’s surface where a compass needle points downwards or upwards, vertically. They aren’t necessarily connected and drawing a line between these points, through the Earth, would not necessarily cross its centre. Therefore, to make better models over time, scientists assume that the Earth is like a bar magnet at its centre, creating poles that are exactly opposite each other – “<a href="https://en.wikipedia.org/wiki/Antipodal_point">antipodal</a>”. This means that if we drew a line between these points, the line would cross directly through the Earth’s centre. At the points where that line crosses the Earth’s surface, we have the geomagnetic poles.</p>
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<img alt="" src="https://images.theconversation.com/files/275107/original/file-20190517-69192-1liuaqx.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/275107/original/file-20190517-69192-1liuaqx.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=341&fit=crop&dpr=1 600w, https://images.theconversation.com/files/275107/original/file-20190517-69192-1liuaqx.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=341&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/275107/original/file-20190517-69192-1liuaqx.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=341&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/275107/original/file-20190517-69192-1liuaqx.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=428&fit=crop&dpr=1 754w, https://images.theconversation.com/files/275107/original/file-20190517-69192-1liuaqx.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=428&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/275107/original/file-20190517-69192-1liuaqx.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=428&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">Positions of the north magnetic pole (red) and the geomagnetic pole (blue) between 1900 and 2020.</span>
<span class="attribution"><a class="source" href="http://www.geomag.bgs.ac.uk/education/poles.html">British Geological Survey</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
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<p>The geomagnetic poles are a kind of reliable, averaged out version of the magnetic poles, which move erratically all the time. Because of that, it turns out they aren’t moving anywhere near as fast as the magnetic north pole is. And since the aurora seems to follow the more averaged version of the magnetic field, it means that the northern lights aren’t moving that fast either. It seems as though the aurora are staying where they are – at <a href="https://theconversation.com/dont-panic-the-northern-lights-wont-be-turning-off-anytime-soon-72436">least for now</a>. </p>
<p>We already know that the magnetic pole moves. Both poles have wandered ever since the Earth existed. In fact, the poles even flip over, with north becoming south and south becoming north. These magnetic reversals have occurred throughout history, every 450,000 years or so on average. The last reversal occurred 780,000 years ago meaning we <a href="https://theconversation.com/why-the-earths-magnetic-poles-could-be-about-to-swap-places-and-how-it-would-affect-us-71910">could be due a reversal soon</a>. </p>
<p>So rest assured that a wandering pole, even a fast one, shouldn’t cause too many problems – except for those scientists whose job it is to model it.</p><img src="https://counter.theconversation.com/content/117237/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. </span></em></p>As the Earth’s magnetic north pole heads towards Siberia, concerns have been raised that the northern lights could move with it.Nathan Case, Senior Research Associate in Space and Planetary Physics, Lancaster UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1128862019-03-06T12:23:01Z2019-03-06T12:23:01ZOur space weather mission will venture deeper into space than any other – here’s what it could achieve<figure><img src="https://images.theconversation.com/files/261894/original/file-20190304-92280-ihwnis.png?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Lagrange mission.</span> <span class="attribution"><span class="source">ESA/A. Baker</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>You may have noticed that some weather forecasts have started mentioning the <a href="https://aurorawatch.lancs.ac.uk/">chances of seeing an aurora</a>, also known as northern lights. Just as the atmosphere of the Earth gives us terrestrial weather, the nearby, vast atmosphere of the sun gives rise to space weather – <a href="https://theconversation.com/what-caused-those-spectacular-northern-lights-and-how-you-can-catch-them-next-time-39081">triggering events such as auroras</a>. Many weather institutes around the world now provide <a href="https://theconversation.com/why-were-preparing-weather-forecasts-in-space-32638">forecasts of the weather in space</a> because of the hazard it poses to services we rely on, such as satellite positioning services, power distribution and communications. </p>
<p>But forecasting services are only as good as the modelling and the data that underpin them. Currently, space weather forecasting satellites typically record this data from their orbit around the Earth. However, working with the UK and the European Space Agencies, we are developing a new satellite, <a href="https://www.esa.int/Our_Activities/Operations/Space_Situational_Awareness/Lagrange_mission_providing_solar_warning">dubbed Lagrange</a>, that could significantly improve space weather predictions. It will venture further away from our planet than any other dedicated space weather mission, getting a much a better view of what is going on. </p>
<p>Extreme space weather storms now feature on the <a href="https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/61934/national_risk_register.pdf">national risk registers</a> of many countries as one of the greatest natural hazards. In the UK, it comes after pandemic flu, coastal flooding and effusive volcanic eruptions. As a result, the Met Office has been monitoring space weather 24 hours a day, every day of the year, since 2014 in order to provide forecasts to a range of customers. Today, severe space weather storms are estimated to have the potential to cause <a href="https://theconversation.com/how-space-weather-poses-a-risk-to-the-finance-industry-64621">billions of pounds of damage</a> across Europe. </p>
<h2>Stable points in space</h2>
<p>Lagrange will carry all the equipment needed to characterise the activity of the sun that determine the conditions in its atmosphere. There are instruments to measure the magnitude of bursts of X-rays called <a href="https://hesperia.gsfc.nasa.gov/sftheory/flare.htm">solar flares</a> and the gusty and variable particle flows and magnetic field of the <a href="https://theconversation.com/solar-wind-and-space-dust-create-new-source-of-water-laboratory-study-suggests-22212">solar wind</a>. Others will detect gigantic eruptions of plasma known as <a href="https://www.swpc.noaa.gov/phenomena/coronal-mass-ejections">coronal mass ejections</a> that dwarf the Earth when they arrive, with streams of particles moving at near light speed.</p>
<p>The whole suite of instruments is cleverly chosen to enable us to monitor and forecast space weather from the sun impacting on the Earth. In particular, it will measure the magnetic fields of the sun that are responsible for creating space weather in the first place and estimate how long it takes the worst space weather to reach the Earth.</p>
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<img alt="" src="https://images.theconversation.com/files/261891/original/file-20190304-92304-2hzil0.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/261891/original/file-20190304-92304-2hzil0.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=512&fit=crop&dpr=1 600w, https://images.theconversation.com/files/261891/original/file-20190304-92304-2hzil0.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=512&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/261891/original/file-20190304-92304-2hzil0.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=512&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/261891/original/file-20190304-92304-2hzil0.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=643&fit=crop&dpr=1 754w, https://images.theconversation.com/files/261891/original/file-20190304-92304-2hzil0.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=643&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/261891/original/file-20190304-92304-2hzil0.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=643&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">Lagrange points.</span>
<span class="attribution"><span class="source">wikipedia</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
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<p>The really new aspect of the mission though is where it will be placed. Rather than being in orbit around the Earth, the spacecraft will be sent to a “Lagrange point”. Massive objects, such as planets, have a strong gravitational field that enables us to put satellites into orbit around them. What is less well known is that that there are positions where the gravitational forces of objects such as the sun and the Earth (including the moon) and orbital motions of a spacecraft interact to create a stable location. When it comes to the sun-Earth system there are five such points, and they are called <a href="https://www.space.com/30302-lagrange-points.html">Lagrange points </a> after the Italian-French mathematician Joseph-Louis Lagrange. </p>
<p>Our mission will hover at the fifth Lagrange point (L5), sitting at one vertex of an equilateral triangle that has the sun and the Earth at its other two points. Putting a spacecraft at L5 essentially gives space weather forecasters a side-on view of the sun that will enable us to see what eruptions are heading towards the Earth. Another advantage is that the spacecraft gets to bathe in solar wind streams that will be directed at the Earth a few days later, due to the rotation of the sun. </p>
<p>Measuring the solar wind flow a few days before it points at the Earth will improve the forecast of background conditions by 50%, helping us accurately forecast an “all clear”. It will also tell us whether Earth-directed coronal mass ejections will be sped up or slowed down by the solar wind through which they move. Together with the side-on view, this will help us more accurately predict the arrival of these large eruptions at the Earth. In fact, it should double the accuracy of the forecast time compared to the current methods.</p>
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<img alt="" src="https://images.theconversation.com/files/261898/original/file-20190304-92301-a8b46s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/261898/original/file-20190304-92301-a8b46s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/261898/original/file-20190304-92301-a8b46s.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/261898/original/file-20190304-92301-a8b46s.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/261898/original/file-20190304-92301-a8b46s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/261898/original/file-20190304-92301-a8b46s.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/261898/original/file-20190304-92301-a8b46s.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">
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<span class="caption">Sun after an eruption.</span>
<span class="attribution"><span class="source">ESA/ROB</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
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<p>The ultimate aim of Lagrange is to improve the resilience of the planet to extreme space weather risk by enabling more accurate forecasts. However a forecast is only useful if those impacted by the hazard know what to do when an alert is issued. The academic community is supporting Lagrange by also responding to this educational space weather need, providing new teaching programmes to enable the key people to gain necessary knowledge and skills to tackle any extreme space weather events in the future. </p>
<p>Responding to extreme space weather can take many forms, but the best protection is to be prepared. If we know a major space weather event is about to happen, then satellite operators can put satellites into “safe mode” to ride out the storm. Meanwhile electricity grid operators can stabilise the grid by reducing repair work and asking high-usage customers such as factories to reduce activity. They can also keep a close eye on the performance of the high-voltage transformers at electricity substations to make sure they are not overheating. </p>
<p>Lagrange is undergoing development at the moment, but all going well it should will launch in the mid-2020s. Given the cost of space weather to our economy, it can’t come a moment too soon.</p><img src="https://counter.theconversation.com/content/112886/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Lucie Green receives funding from the Royal Society. </span></em></p><p class="fine-print"><em><span>Robert Wicks receives funding from HEFCE, STFC, and UKSA. </span></em></p>The Lagrange mission could greatly improve forecasts of space weather.Lucie Green, Professor of Physics, UCLRobert Wicks, Lecturer in Space Risks, UCLLicensed 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>
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<p><strong>What causes the northern lights? – Ffion, age 6.75, Pembrokeshire, UK.</strong></p>
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<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>
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<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">
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<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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<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/761952017-04-21T20:30:02Z2017-04-21T20:30:02ZWater, weather, new worlds: Cassini mission revealed Saturn’s secrets<figure><img src="https://images.theconversation.com/files/166237/original/file-20170421-12662-1kfv8oj.jpg?ixlib=rb-1.1.0&rect=563%2C8%2C1718%2C1354&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Saturn and its rings backlit by the sun, which is blocked by the planet in this view. Encircling the planet and inner rings is the much more extended E-ring.</span> <span class="attribution"><span class="source">NASA/JPL/Space Science Institute</span>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p><a href="https://saturn.jpl.nasa.gov">Cassini</a> is the most sophisticated space probe ever built. Launched in 1997 as a joint NASA/European Space Agency mission, it took seven years to journey to Saturn. It’s been orbiting the sixth planet from the sun ever since, sending back data of immense scientific value and images of magnificent beauty.</p>
<p>Cassini has begun one last campaign. Dubbed <a href="https://saturn.jpl.nasa.gov/mission/grand-finale/overview/">the Grand Finale</a>, it will end on Sept. 15, 2017 with the probe plunging into Saturn’s atmosphere, where it will burn up. Although Saturn <a href="https://solarsystem.nasa.gov/missions/pioneer11/indepth">was visited</a> by <a href="http://voyager.jpl.nasa.gov">three spacecraft</a> in the 1970s and 1980s, <a href="https://saturn.jpl.nasa.gov/mission/team/">my fellow scientists and I</a> couldn’t have imagined what the Cassini space probe would discover during its sojourn at the ringed planet when it launched 20 years ago.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/166306/original/file-20170421-12645-14drs45.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/166306/original/file-20170421-12645-14drs45.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/166306/original/file-20170421-12645-14drs45.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/166306/original/file-20170421-12645-14drs45.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/166306/original/file-20170421-12645-14drs45.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/166306/original/file-20170421-12645-14drs45.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/166306/original/file-20170421-12645-14drs45.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/166306/original/file-20170421-12645-14drs45.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">A huge storm churning across the face of Saturn. At the time this image was taken, 12 weeks after the storm began, it had completely wrapped around the planet.</span>
<span class="attribution"><a class="source" href="https://saturn.jpl.nasa.gov/resources/5329/">NASA/JPL-Caltech/SSI</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<h2>A planet of dynamic change</h2>
<p>Massive storms periodically appear in Saturn’s cloud tops, known as Great White Spots, observable by Earthbound telescopes. Cassini has a front-row seat to these events. We have discovered that just like Earth’s thunderstorms, these storms contain <a href="https://saturn.jpl.nasa.gov/resources/4943/">lightning</a> and hail. </p>
<p>Cassini has been orbiting Saturn long enough to observe seasonal changes that cause variations in its weather patterns, not unlike the seasons on Earth. Periodic storms often appear in late summer in Saturn’s northern hemisphere. </p>
<p>In 2010, during northern springtime, an unusually early and intense storm appeared in Saturn’s cloud tops. It was a storm of such immensity that it <a href="http://doi.org/10.1016/j.icarus.2012.12.013">encircled the entire planet</a> and lasted for almost a year. It was not until the storm ate its own tail that it eventually sputtered and faded. Studying storms such as this and comparing them to similar events on other planets (think Jupiter’s Great Red Spot) help scientists better understand weather patterns throughout the solar system, even here on Earth. </p>
<p>Having made hundreds of orbits around Saturn, Cassini was also able to deeply investigate other features only glimpsed from Earth or earlier probes. <a href="https://saturn.jpl.nasa.gov/mission/spacecraft/navigation/">Close encounters with Saturn’s largest moon, Titan</a>, have allowed navigators to use the moon’s gravity to reorient the probe’s orbit so that it could swing over Saturn’s poles. Because of <a href="https://saturn.jpl.nasa.gov/science/magnetosphere/">Saturn’s strong magnetic field</a>, the poles are home to <a href="https://saturn.jpl.nasa.gov/resources/4452/">beautiful Aurorae</a>, just like those of Earth and Jupiter.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/166304/original/file-20170421-22929-dgvpi6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/166304/original/file-20170421-22929-dgvpi6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/166304/original/file-20170421-22929-dgvpi6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/166304/original/file-20170421-22929-dgvpi6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/166304/original/file-20170421-22929-dgvpi6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/166304/original/file-20170421-22929-dgvpi6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/166304/original/file-20170421-22929-dgvpi6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/166304/original/file-20170421-22929-dgvpi6.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">Saturn’s six-sided vortex at Saturn’s north pole known as ‘the hexagon.’ This is a superposition of images taken with different filters, with different wavelengths of light assigned colors.</span>
<span class="attribution"><span class="source">NASA/JPL-Caltech/SSI/Hampton University</span>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Cassini has also confirmed the existence of a bizarre <a href="https://saturn.jpl.nasa.gov/news/2509/nasas-cassini-spacecraft-obtains-best-views-of-saturn-hexagon/">hexagon-shaped polar vortex</a> originally glimpsed by the Voyager mission in 1981. The vortex, a mass of whirling gas much like a hurricane, is larger than the Earth and has top wind speeds of 220 mph. </p>
<h2>Home to dozens of diverse worlds</h2>
<p>Cassini discovered that Saturn has 45 more moons than the 17 previously known – placing the total now at 62.</p>
<p>The largest, <a href="https://saturn.jpl.nasa.gov/science/titan/">Titan</a>, is bigger than the planet Mercury. It possesses a dense nitrogen-rich atmosphere with a surface pressure one and a half times that of Earth’s. Cassini was able to probe beneath this moon’s cloud cover, discovering rivers flowing into lakes and seas and being replenished by rain. But in this case, the liquid is not water, but rather liquid methane and ethane.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/166307/original/file-20170421-22929-1ieknjz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/166307/original/file-20170421-22929-1ieknjz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/166307/original/file-20170421-22929-1ieknjz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=572&fit=crop&dpr=1 600w, https://images.theconversation.com/files/166307/original/file-20170421-22929-1ieknjz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=572&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/166307/original/file-20170421-22929-1ieknjz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=572&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/166307/original/file-20170421-22929-1ieknjz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=719&fit=crop&dpr=1 754w, https://images.theconversation.com/files/166307/original/file-20170421-22929-1ieknjz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=719&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/166307/original/file-20170421-22929-1ieknjz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=719&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">False-color image of Ligeia Mare, the second largest known body of liquid on Saturn’s moon Titan. It’s filled with liquid hydrocarbons.</span>
<span class="attribution"><a class="source" href="https://saturn.jpl.nasa.gov/news/2824/titan-flyby-t-93-monitoring-the-lakes/">NASA/JPL-Caltech/ASI/Cornell</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>That’s not to say that water is not abundant there – but it’s so cold on Titan (with a surface temperature of -180°C) that water behaves like rock and sand. Although it has all the ingredients for life, Titan is essentially a “frozen Earth,” trapped at that moment in time before life could form.</p>
<p>The sixth-largest moon of Saturn, <a href="https://saturn.jpl.nasa.gov/science/enceladus/">Enceladus</a>, is an icy world about 300 miles in diameter. And for me, it’s the site of the Mission’s most spectacular finding.</p>
<p>The discovery started humbly, with a curious blip in magnetic field readings during the first flyby of Enceladus in 2004. As Cassini passed over the moon’s southern hemisphere, it detected strange fluctuations in Saturn’s magnetic field. From this, the Cassini magnetometer team inferred that Enceladus must be a source of ionized gas.</p>
<p>Intrigued, they instructed the Cassini navigators to make an even closer flyby in 2005. To our amazement, the two instruments designed to determine the composition of the gas that the spacecraft flies through, the <a href="https://saturn.jpl.nasa.gov/cassini-plasma-spectrometer/">Cassini Plasma Spectrometer (CAPS)</a> and the <a href="https://saturn.jpl.nasa.gov/ion-and-neutral-mass-spectrometer/">Ion and Neutral Mass Spectrometer (INMS)</a>, determined that Cassini was unexpectedly passing through a cloud of ionized water. Emanating from cracks in the ice at Enceladus’ south pole, these water plumes gush into space at speeds up to 800 mph. </p>
<p>I am on the team that made the <a href="https://doi.org/10.1126/science.1121061">positive identification of water</a>, and I have to say it was the most thrilling moment in my professional career. As far as Saturn’s moons were concerned, everyone thought all of the action would be at Titan. No one expected small, unassuming Enceladus to harbor any surprises.</p>
<p>Geologic activity happening in real time is quite rare in the solar system. Before Enceladus, the only known active world beyond Earth was <a href="http://www.space.com/16419-io-facts-about-jupiters-volcanic-moon.html">Jupiter’s moon Io</a>, which possesses erupting volcanoes. To find something akin to Old Faithful on a moon of Saturn was practically unimaginable. The fact that it all started with someone noticing an odd reading in the magnetic field data is a wonderful example of the serendipitous nature of discovery.</p>
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<a href="https://images.theconversation.com/files/166303/original/file-20170421-12650-nds7qd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/166303/original/file-20170421-12650-nds7qd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/166303/original/file-20170421-12650-nds7qd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=350&fit=crop&dpr=1 600w, https://images.theconversation.com/files/166303/original/file-20170421-12650-nds7qd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=350&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/166303/original/file-20170421-12650-nds7qd.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=350&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/166303/original/file-20170421-12650-nds7qd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=439&fit=crop&dpr=1 754w, https://images.theconversation.com/files/166303/original/file-20170421-12650-nds7qd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=439&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/166303/original/file-20170421-12650-nds7qd.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=439&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 geyser basin at the south pole of Enceladus, with its water plumes illuminated by scattered sunlight.</span>
<span class="attribution"><span class="source">NASA/JPL-Caltech/Space Science Institute</span>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>The story of Enceladus only becomes more extraordinary. In 2009, the plumes were directly imaged for the first time. We now know that water from Enceladus comprises the largest component of Saturn’s magnetosphere (the area of space controlled by Saturn’s magnetic field), and the plumes are responsible for the very existence of Saturn’s vast <a href="https://saturn.jpl.nasa.gov/resources/3276/">E-ring</a>, the second outermost ring of the planet.</p>
<p>More amazingly, we now know that beneath the crust of Enceladus is a global ocean of liquid saltwater and organic molecules, all being heated by hydrothermal vents on the seafloor. Detailed analysis of the plumes show they contain hydrocarbons. All this points to the possibility that Enceladus is an ocean world harboring life, right here in our solar system. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/xrGAQCq9BMU?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">NASA at Saturn: Cassini’s Grand Finale.</span></figcaption>
</figure>
<p>When Cassini plunges into the cloud tops of Saturn later this year, it will mark the end of one of the most successful missions of discovery ever launched by humanity.</p>
<p>Scientists are now considering targeted missions to Titan, Enceladus or possibly both. One of the most valuable lessons one can take from Cassini is the need to continue exploring. As much as we learned from the first spacecraft to reach Saturn, nothing prepared us for what we would find with Cassini. Who knows what we will find next?</p><img src="https://counter.theconversation.com/content/76195/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Dan Reisenfeld receives funding from NASA. </span></em></p>With the probe now on its ‘Grand Finale,’ a Cassini team member describes the amazing discoveries it made about the ringed planet and its many moons.Dan Reisenfeld, Professor of Physics & Astronomy, University of MontanaLicensed as Creative Commons – attribution, no derivatives.