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  Coming and going like the solar windJul 21, 2011 5:54 AM PDT | url
 
Added 1 new A* page:I think it was in looking for movies showing visualizations of the Sun's magnetosphere or something, in relation to the recent Voyager findings I was discussing last week, that I came across this video, showing visual readings from various NASA craft, etc, from May 10-12, 1999, which NASA called The Day the Solar Wind Disappeared:
 
video on Youtube
 
In that period, solar wind activity decreased by 98%, and electrons directly from the Sun's corona, usually broken up and dispersed by the solar wind, were able to shoot along magnetic lines to Earth in beams known as strahl, which is a funny word; these in turn came down Earth's magnetic lines to the poles, causing an unusual auroral event dubbed "polar rain." And in the absence of pressure from the solar wind, the Earth's magnetosphere was able to swell to over five times its normal size.
 
Interesting! But why this dramatic change, so dramatic as to cause some to say it shows the Sun is a "variable" star? In the end I had to go dig through some academic papers on the event by primary researcher P. Janardhan; in this 2008 paper, the team says that this was conclusive proof of "non-explosive" solar events having effects on "space weather" as far out as Earth, and concludes that (I may be understanding this wrong, mind you--there are a lot of charts and big words I don't quite follow) the cut-off of solar wind was caused by active regions on the Sun's surface magnetically connecting with, and effectively "pinching" off, the coronal hole through which the wind would ordinarily have been issuing.
 
This abstract of a later article headed by Janardhan mentions that similar "solar wind disappearance events" occurred in March and May 2002.
 
A stellar active region is just a fancy name for a place on the Sun's surface where something is going on other than just normal, relatively quiescent heat and magnetism; sun spots, for instance, are active regions characterized by a depressed altitude and temperatures as low as half of the surrounding surface, which causes them to look dark due to some black body radiation science I don't quite follow. The Wikipedia article notes that such areas on other stars are properly called starspots, and says that the Sun's are relatively tiny compared to those seen on other stars, which have been observed to cover as much as 30% of the star's surface!
 
Here's a nifty highly magnified view of a "planet-sized" sunspot from 2002; taken by the Swedish Solar Telescope in the Canary Islands, whose 98 cm lens makes it the second largest optical refracting telescope in operation, and which operates in a vacuum to prevent distortion by heated air--a particular problem for solar telescopes since all that light they take in heats things up; this was, at the time, the sharpest view of the Sun ever taken, and the first photo revealing long "filaments" going into a sunspot:
 
Image
image by NASA (source)
 
 
 
 
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