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Thursday, October 02, 2008

The Quiescent Sun

By sheer coincidence there is an article in today's Financial Times regarding the current inactivity of the Sun. It is a nice article minus the hyperbole that seems to often surround discussion of this current solar minimum.


Back on Earth, the Sun’s inactivity ought to represent good news for the companies that operate satellites, run power grids or make terrestrial radio systems, which are all vulnerable to damage and disruption from solar storms. In one interpretation of its long-term implications, however, the effects could be far from benign.

True enough. The article does make the point that big storms can still happen at solar minimum and so complacency should be avoided. It reminds us of the Carrington event:

What astronomers believe was the most intense eruption from the Sun for several centuries took place in August 1859 during an otherwise fairly tranquil solar cycle. The aurora borealis or Northern Lights – the vivid photoelectric display triggered when solar particles hit Earth’s upper atmosphere – moved down from its normal polar haunts to put on a spectacular show as far as the tropics. Other effects included putting the world’s nascent telegraph network out of action for several hours.

If such a solar superstorm occurred now, it would cause tens of billions of dollars of damage to communications and navigational satellites and cause continent-wide electrical blackouts that might last for weeks, say Sten Odenwald and James Green, Nasa scientists who have analysed the 1859 event.

Nothing like this has happened in the Space Age, the closest was a big storm in October 1989. Of course knowing that events like these occur is no part of a justification for funding into investigating this highly important and societally relevant topic.

The CEO of STFC is on record as saying that if we lived in a world where a big storm had occurred STP would be properly regarded, but we don't live in that world so cutting funding is justified. Indeed others think that we STPers argue that the October 1989 storm is our main excuse for studying STP, a claim so asinine and moronic that it stunned a scientific audience into silence.

Anyway, climate popped up in the FT article:
Experts are reluctant to predict the consequences for Earth and its inhabitants because there are so many complex interactions between the Sun’s output, the planet’s atmosphere and magnetic field, and cosmic radiation from outer space. Some climatologists say that, over a period of decades, a quieter Sun means a cooler Earth, although the relationship between solar activity and climate is particularly controversial.

Controversial is not a word I would use. Rather I would suggest that the relationship is poorly understood.

There is a clear link between the Sun's activity and climate and contrary to what some believe this is accounted for by climatologists. There have been some recent hypotheses that suggest that recent climate change can be placed totally (or nearly so) on the Sun (the article mentions this near the end) but the evidence has been far from compelling unless you have the 'eye-of-faith*'.

What is needed is a better understanding of the mechanisms by which the Sun affects the Earth environment so that we can put proper numbers and limits on the effect. By wanting to study the link most scientists have no agenda; we aren't trying to 'prove' that the global warming sceptics are right, nor are we trying to prove the manmade CO2 hypothesis correct. Rather we just want to know what affect there is and how it works, maybe it is huge and dominates over anthropogenic effects (I doubt it) or maybe it is quite small but important for staving off the worst effects of CG during a solar-quiet period.

Of course, one side product of the quiet sun is that we have had lots of nice, sustained, coronal holes that lead to high speed solar wind streams and high latitude auroral displays. This is nice for my research as I am looking at energy input to the magnetosphere during these events and how it is distributed throughout the system.


Another interesting aspect of the solar minimum mentioned in the FT article is the hazards to manned space travel:

This quiet period would not be a good time to launch a manned space mission beyond Earth orbit, to the Moon or Mars, adds Prof Crooker. Astronauts would face the harmful impact of increased cosmic radiation, which would outweigh the reduced likelihood of solar storms.
It is easy to think that now is the best time to launch manned missions out beyond the protective magnetosphere but the truth is that the issue is more complex than that. At solar maximum the solar wind affords better protection from the constant, though relatively weak, bombardment of cosmic rays. Huge flares and CMEs at solar maximum can cause severe damage and are incredibly dangerous, but the sustained exposure to cosmic rays during minimum is arguably the more serious problem.

During transient flares and CMEs astronauts can hide behind appropriate shielding; with a constant bombardment of cosmic rays the astronauts would have to be hiding all the time or risk death (or aquiring super-powers).


The article was nice timing with the release of the Wakeham review, but totally unconnected. I have some thoughts on the Wakeham review report but they can wait until later.

*'eye-of-faith' refers to the ability to look at a scatter plot of data and draw a nice straight line through it representing where you think it should be.

Image of blank solar disc taken by SOHO/MDI, image of coronal hole from the Hinode X-ray Telescope; both hosted by spaceweather.com


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