images

Aurora borealis 10/2003

by

D.Anderson/Novapix

Reference

t-met01-11024

Date

2007-10-26

This image, was taken on October 29, 2003 from Homer, Alaska. It is a very rare blue aurora. Our eyes are not very sensitive to this end of the spectrum so if we are to see the color it has to be especially bright. Blue auroras are caused by the action of sunlight on already-ionized nitrogen molocules in a process known as resonance scattering. In this case the aurora reaches up out of the Earth's shadow into direct sunlight near dawn. This type of emission has been measured 1000km or more into space.