SM31B-2490
The Atmospheric Escape of Europa: The Role of Symmetrical O2 Charge Exchanges.

Wednesday, 16 December 2015
Poster Hall (Moscone South)
Vincent J Dols1, Fran Bagenal2, Timothy A Cassidy1, Frank J Crary1 and Peter A Delamere3, (1)University of Colorado at Boulder, LASP, Boulder, CO, United States, (2)University of Colorado at Boulder, Boulder, CO, United States, (3)University of Alaska Fairbanks, Fairbanks, AK, United States
Abstract:
We model the interaction of magnetospheric plasma with the atmosphere of Europa using a multi-species chemistry model where the atmospheric distributions of H2 and O2 are prescribed. The plasma flow is idealized as an incompressible flow around a conducting obstacle. We compute changes in plasma composition resulting from this interaction as well as the reaction rates integrated over the simulation domain for several upstream plasma conditions (ion density, ion temperature and flow velocity). We show that for all cases, the main atmospheric loss process is the symmetrical charge exchange of O2, which results in the production of fast neutrals. This neutral production rate is about an order of magnitude larger than the production of ions. This conclusion is relevant to future missions to Europa that aim to detect fast neutrals. The neutral ejection resulting from this charge exchange creates an oxygen cloud around the orbit of the moon that is very extended radially but also very tenuous, and has not yet been directly detected.