What is the aurora made of?
The aurora is light: green, blue, red and various combinations. The light is emitted from atoms and molecules of air, that is, mostly oxygen and nitrogen. The atoms and molecules that emit the light have been struck by fast moving electrons that come from outer space. When struck some of the energy of an electron is absorbed by the atom or molecule, leaving it in an excited state. It can’t stand being excited very long, so gives off its extra energy in the form of a photon, or light. If enough atoms and molecules have been struck, that is if the beam of electrons from outer space is sufficiently intense, then enough photons are emitted so that we can see the aurora with our eyes. Since the air atoms and molecules have to be struck by the electrons, they have to be high enough up so that the electrons can reach them. The altitude of the aurora is usually about 90 to 150 km. Now where do these electrons come from? That is another whole question. They probably do not come from the sun lik
