Aurora Australis captured by NASA’s IMAGE satellite and overlaid onto NASA’s satellite-based Blue Marble image. Auroras are caused by solar activity, but the sun doesn’t know what season it is on Earth. So how could one season yield more auroras than another?
“There’s a great deal we don’t understand about auroras,” says UCLA space physicist Vassilis Angelopoulos. For instance, “Auroras sometimes erupt with little warning and surprising intensity. We call these events ‘sub-storms,’ and they are a big mystery.” What triggers the eruptions? Where is sub-storm energy stored? (It has to gather somewhere waiting to power the outburst.)
This is the Aurora Australis, which dances through the sky virtually all the time during the long Antarctic night over Amundsen-Scott South Pole Station. The photo’s surreal appearance makes the station look like a futuristic Mars Station. Photographer Chris Danals, National Science Foundation