Geocorona
Luminous part of the outermost region of the Earth's atmosphere / From Wikipedia, the free encyclopedia
The geocorona is the luminous part of the outermost region of the Earth's atmosphere, the exosphere. It is seen primarily via far-ultraviolet light (Lyman-alpha) from the Sun that is scattered from neutral hydrogen.[1] It extends to at minimum 15.5 Earth radii and probably up to about 100 Earth radii (for context, the Moon is approx. 60 Earth radii away).[2] The geocorona has been studied from outer space by the Astrid satellites and the Galileo spacecraft (among others), using its ultraviolet spectrometer (UVS) during an Earth flyby.