The Absorption of Extreme Ultraviolet Solar Radiation by Jupiter's Upper Atmosphere

Abstract

The absorption of extreme ultraviolet (EUV) sunlight by Jupiter's upper atmosphere is investigated and a detailed description is offered for the collision processes by which photoelectrons lose energy. It is argued that thermal equilibrium between electrons, ions and neutrals is probable at least with current ideas on the structure of Jupiter's ionosphere. An estimate is given for the fraction of absorbed EUV energy converted locally into heat. This estimate, 86%, is considerably larger than a value of 61% computed earlier for the atmospheres of Venus and Mars, a consequence of the comparative absence of radiating levels in gases expected to be present in Jupiter's upper atmosphere.