Incidentally exactly one year ago I was also shooting Aurora Borealis – Northern Lights photos. I recall the conditions were somewhat better than today, but still, I am not complaining. I shot a few, but this was – if not the best – the most interesting because of the perspective. The aurora is partly obscured by a cloud.
Aurora borealis is formed some 80 – 3-400 km above Earth Surface by charged particles from the sun that excites atoms in the ionosphere. When the electrons in the excited atoms falls back again to lower states of energy, they release the energy, from the collision with the particle from the sun, in the form of a photon which is the light waves/particles that we observe as light on our retina.