Aurora, Vermont USA
Photographed by Amber Rahm.
This energetic display in 2002 was not long after a maximum in the eleven year
cycle of solar activity.
Green emission from excited oxygen atoms forms
tall diffuse columns 60 - 90 miles altitude.
Atomic oxygen emissions also formed the reds but higher, more than 90
miles above the earth. At lower altitudes the red emissions are quenched
by gas collisions.