Airglows of many colours
|A different airglow palette. Some green airglow can be seen lighting the sky but the predominant colour is a red/orange, probably high level (150-300km) radiation from excited oxygen atoms.
|Airglow is the light of electronically and/or vibration-rotationally excited atoms and molecules high in Earth's atmosphere..
Aurorae are at similar heights and they too are the light of excited atoms. There is a difference, auroral excitation is by collisions with energetic particles whereas daytime short wavelength solar radiation produces the excitation.
The sun’s extreme ultraviolet light excites oxygen and nitrogen atoms and molecules in the thermosphere*. The energetic products collide and interact with other atmospheric components, including hydroxyl radicals (OH), to eventually produce light emission by chemiluminescence*and the decay of excited atoms and molecules.
Airglow is weak, always weak. Take away manmade light pollution, take away dust and haze, take away moonlight. The final barrier to a sky lit only by the stars is.. ..airglow.