Hot oxygen corona at Europa

A model of the hot oxygen exosphere at Europa was constructed. The source term for the hot atoms was assumed to be dissociative recombination of O₂⁺ and Liouville's theorem was used to calculate their altitude distribution. It was found that near the surface the hot oxygen density is in excess of 200 cm^-3, dropping to a value on the order of 50 cm^-3 at 1500 km. These calculations indicate that the hot atomic oxygen densities are considerably less than the thermal molecular oxygen ones, but slightly larger than the measured sodium values. The escape flux of the hot oxygen atoms was calculated to be on the order of 1.4x10⁸ atoms cm^-2 sec^-1. This corresponds to a global escape rate of 4.4x10²⁵ atoms sec^-1, which is more than an order of magnitude less than the estimated atmospheric sputtering rate.