Curtain of Aurora Above Spruce Forest, Alaska
Interior Alaska
A long vertical curtain of bright green aurora borealis, with pink tints along the lower edge, falls from the top of the frame down to a spruce forest silhouette in Interior Alaska. This kind of single isolated curtain usually means the display is either just starting or just settling, and it is often the cleanest composition of a whole aurora night. The pink lower edge is caused by nitrogen emission in the bottom part of the curtain where the energetic particles reach lower and denser air. When the conditions are right you get this layered color look for free. Aurora borealis, Alaska. Photo © copyright by Carl Donohue.
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