It's from Astronomy Pic of the Day
http://antwrp.gsfc.nasa.gov/apod/ap021114.html
If you click on the image there, you get the larger version.
Further investigation of their links suggest that it really came from here
http://www.solarphysics.kva.se/
Where they say you can use the images if you give credit to the Royal Swedish Academy of Sciences. So here goes: "That Royal Swedish Academy of Sciences, boy I gotta hand it to them. They really know how to teach that science. In a Swedish and royal way. I gotta give them credit."