While you might think the sun has pretty much just one weather pattern – blistering and violent with a chance of radiation poisoning – it can actually be quite varied. One of the lesser-known weather phenomena on the sun's surface are coronal holes, like the massive one that was recently captured by NASA's Solar Dynamics Observatory (SDO) and featured this week in a short video from the space agency.
"Coronal holes are low-density regions of the sun's atmosphere, known as the corona," says NASA. "Because they contain little solar material, they have lower temperatures and thus appear much darker than their surroundings. Coronal holes are visible in certain types of extreme ultraviolet light, which is typically invisible to our eyes, but is colorized here in purple for easy viewing." The holes are also visible in x-ray wavelengths.
Although it's not clear what causes the coronal holes to appear on the sun, it is known that the patches are the source of a super-fast solar wind that can be up to three times more rapid than solar winds from other parts of the sun. The solar wind is a stream of plasma containing charged particles that shoots off the sun. When such a stream contacts the Earth's magnetosphere, it can cause storms that lead to pleasant results like the aurora borealis, or more destructive results like disrupting power supplies and communications.
During solar minimums – approximately 11-year-long periods during which the sun is relatively quiet – coronal holes appear near the solar poles, as this one does. That makes sense because this video was created from images taken by the SDO in early May, and we are currently on the downslope from a solar maximum that peaked in 2013, and was itself relatively weak.
The SDO was launched in 2010 and consists of a series of instruments specifically designed to observe the sun. It has been returning some pretty astounding images since being put into orbit around Earth.
This video showing the coronal hole adds to the impressive eye-candy the SDO has been sending back of our nearest and dearest star for much of the decade.
Source: NASA