A brilliant green section of the aurora borealis in its arc form
shines over the skies of the Alaskan wilderness, a prime spot for
aurora watching. This aurora occurred in the fall, when
sky-watchers often report seeing auroras. Scientists don't yet
know why, but geomagnetic storms that ignite auroras tend to
happen more frequently during the months surrounding the fall and
spring equinoxes. Green auroras like this one are the result of
energized oxygen located 150 miles or less above Earth's surface.