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 these are higher, more than 90 miles above the earth. At lower altitudes the red emissions are quenched by gas collisions.