It would appear that the blue sky is actually produced by the solar wind and solar radiation exciting air molecules to emit light, just like a neon lamp!

— Steven Magee
airastrobiologyastronomicalastronomyastrophysicsblueblue-skyemitexciteexcitementexcitinglamplightmoleculesneonneon-lightradiationradiation-effectssolarsolar-energysolar-powersolar-systemwind