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Why is the sun going quiet?

The sun is our nearest star and the source of all our light and heat on Earth but recent reports have highlighted an ongoing steep decline in solar activity. This story is a reminder that our sun is a…

What’s going on up there? VinothChandar

The sun is our nearest star and the source of all our light and heat on Earth but recent reports have highlighted an ongoing steep decline in solar activity.

This story is a reminder that our sun is a variable star whose dynamic production of magnetism, activity and winds have implications for our planet.

Solar magnetic fields power solar activity, including sunspots, explosive events known as solar flares and coronal mass ejections, and an outward-flowing solar wind.

The sun’s activity and wind bathes Earth in a changing space environment of high-energy radiation and fast-moving particles called “space weather”. This gives us both the beauty of the aurorae and disruptive effects on communications and other technology.

Solar activity varies over time, with the 11-year sunspot cycle being the most familiar example. Solar activity also varies more widely over longer timescales, producing “grand maxima” and “grand minima”.

NASA

The most famous of these is the Maunder minimum in sunspot activity from around 1645 to 1715.

The current rate and extent at which solar activity is falling has been interpreted as the beginning of another grand minimum, and raises the issue of what it means for Earth’s climate.

Variations in solar activity have long been linked to climate variability on Earth, with the most familiar historical example being the Maunder minimum. This corresponded to relatively cold climatic conditions described as the “Little Ice Age” when rivers that were normally ice-free froze and snow fields remained year-round at lower altitudes.

Question of how solar activity influences the Earth’s climate remains the subject of ongoing research. What is becoming clearer is that variations in solar ultraviolet radiation resulting from solar activity can provide a physical mechanism for the Sun to influence the Earth’s atmosphere.

However, it is important to understand that research also indicates that these solar effects are minor compared to modern-day anthropogenic effects. Even if there is measurable cooling, a grand minimum should not be relied upon to slow global warming.

Climatic effects aside, a grand minimum in solar activity would mean reduced auroral displays, and some lessening of the hazards caused by space weather for spacecraft, and any occupants.

Why the fluctuations?

The convoluted magnetic field lines extending from the sun. NASA

The answer lies in how the sun generates its magnetic field.

As a typical star our sun is a ball of hot gas, more than a hundred times the diameter and hundreds of thousands of times more massive than the Earth.

Inside the sun, the effects of heat, pressure and motion produce electrical currents that in turn generate magnetic fields. This solar dynamo results in magnetic fields emerging from the sun’s visible surface to power its activity and winds and the space weather experienced by Earth.

Explaining the variable nature of solar activity comes down to understanding the physics of the solar dynamo. At present there is a general theoretical picture of how the dynamo can produce magnetic fields and even cycles.

What is less certain is how the dynamo changes into the special state that corresponds to grand minimum, and whether such occurrences are to some extent predictable or purely random.

One way to learn more about the sun and its dynamo is to study other stars. Dynamos occur in many other stars, so observations of stars of different ages can offer clues regarding the past and future of solar magnetism and its effects. These magnetic studies of stars and their activity and winds can be used to better test the predictions of dynamo theory.

An improved understanding of stellar dynamos may then help us know more about what is happening to the sun today, and perhaps provide a useful tool to forecast future changes in our variable sun.

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  1. David K Clarke

    logged in via Facebook

    Whether the Maunder Minimum coincides with the Little Ice Age seems to be at least partly a matter of opinion.

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    1. Felix MacNeill

      Environmental Manager

      In reply to David K Clarke

      I gather, also, that the 'Little Ice Age' was a rather localised phenomonon, rather than global: the Thames may have frozen and so forth, but effects weren't experienced everywhere.

      As the article very sensibly suggests, even if we were at the beginning of another minimum and even if a minimum did have a clear cooling effect, it would still be far too little to counter-balanced anthropogenic impacts. Indeed, if anything, it may be slightly masking existing anthropogenic impacts.

      It's a bit…

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    2. Henry Verberne

      Once in the fossil fuel industry but now free to speak up

      In reply to Felix MacNeill

      "It's a bit like the way fools use the relatively flat surface temperature line than can be drawn on a graph, rather arbitrarily, from 1998 to the present, as 'evidence' that global warming has stalled or sensitivity is lower than anticipated".

      As much as I's like to attribute this to incompetence rather than malice, I think that some extreme contrarians nothwithstanding, a substantial number of deniers know full well that they are spreading misinformation. Its an orchestrated campaign.

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    3. Jonathan Maddox
      Jonathan Maddox is a Friend of The Conversation.

      Software Engineer

      In reply to David K Clarke

      I've read that the onset of the Little Ice Age also coincides with a drop in atmospheric CO2 and with the "germs" part of "Guns, Germs and Steel", in that a large portion of the native population of the Americas died from the diseases of contact, starting in the early 17th century.

      The theory goes that after the people died, their cleared, cultivated and grazed lands reverted to forest -- drawing down a significant amount of carbon dioxide from the atmosphere and yes, triggering the Little Ice Age.

      https://www.sciencenews.org/article/columbus-arrival-linked-carbon-dioxide-drop

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    4. Jim Inglis

      retired

      In reply to Felix MacNeill

      "I gather, also, that the 'Little Ice Age' was a rather localised phenomonon, [sic]"

      Felix,if you look around you might find some much better science:

      http://hockeyschtick.blogspot.com.au/2012/05/new-paper-confirms-little-ice-age-was.html

      "It's a bit like the way fools use the relatively flat surface temperature line than can be drawn on a graph, rather arbitrarily, from 1998 to the present, as 'evidence' that global warming has stalled"

      I know you have a preference for the manipulated…

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    5. In reply to Jim Inglis

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  2. Jack Arnold

    Polymath

    An interesting introduction to an obviously complex field. But at a practical level ... what is the link between solar activity in its many forms and the formation of weather features like high pressure ridges and low depressions?

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    1. Jack Arnold

      Polymath

      In reply to Jack Arnold

      Hmmm ... six removals ... impressive.

      Perhaps I should have disclosed a forty (40) year interest in weather forecasting that has yet to discover the true cause(s) of weather variations in my location.

      Great article BTW, look more closely at solar flares and the Inigo Jones approach to long range weather forecasting. I am advised his records still exist in Queensland. Then, there may also be a website.

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  4. Fred Smith

    Electrical Engineer

    Interesting article, thanks for that.

    Your link that states minor effects is a press release from 2004. This release says there is further research being done. It would be nice if you could follow up what has been happening over the last 9.5 years in this area. Your ongoing research link shows its current data as 2000 (both the mpg.de links).

    More current info would be nice if you have time.

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    1. Fred Smith

      Electrical Engineer

      In reply to Fred Smith

      Edit: your new scientist and NASA links are a bit better with data, still a bit more analysis would be nice. The new scientist article states that the last grand solar maximum peaked in 1956, and that the cycles are around 400 years on average.

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  5. Stephen H

    In a contemplative fashion...

    Brad, please correct your first sentence. It makes an absolute statement that ignores other sources such as radiation inside the Earth, distant stars etc. A simple "almost" would do.

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  6. Jim Inglis

    retired

    The CET which includes most of the Maunder Minimum, while it is local temp, it ties in very well with all the temp records for the ROW that came after.

    It shows a steady warming of less than 1c since 1659.

    When CO2 emissions started to grow in 1946 it shows the complete lack of correlation between this steady, small growth in warming over the last 350 years with the huge growth in ACO2 over the last 60 odd years.

    IOW, it puts a serious question mark over the GHG theory:

    http://wattsupwiththat.files.wordpress.com/2011/11/tbrown_figure3.png

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    1. In reply to Jim Inglis

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    4. In reply to Mike Jubow

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    5. In reply to Jim Inglis

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