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.