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| Image generated by AI using Bing Image Creator |
Usually green and pink, but sometimes blue. The display is effectively like a giant fluorescent tube (which is a type of discharge lighting, along with sodium and mercury vapour lamps, used for street lighting.) Just like the way a neon lamp emits pink or red-orange light as electrons flowing through the tube collide with neon atoms in the lamp (an electric current is simply a flow of electrons), high energy charged particles from the Sun hit the atmosphere, causing various gases to fluoresce and emit light of different colours. Green is produced by oxygen and red and pink are produced by oxygen at higher altitudes. Blue, purple, and pinkish-red colours are produced by nitrogen.
Electrons exist in orbitals which are shells or zones surrounding the nuclei of atoms. Photons (particles of light) are emitted by electrons when they get excited and move to higher orbitals and then return back to their normal state. That excitation can come from heating, e.g. an iron bar in a fire gets red or yellow hot. It can also occur when particles from the Sun, typically electrons and protons, strike gasses in the atmosphere. If solar particles are energetic enough (travelling sufficiently fast), they can strip electrons off atoms, creating what are known as ions.That’s similar to what happens in the gaps of a vehicle’s spark plugs or during a lightning flash, where air breakdown occurs and electrons liberated from atoms collide with others, resulting in an avalanche and breakdown of the air gap.
More info here:
https://www.space.com/aurora-colors-explained
