Quantifying the access of Jupiter's magnetospheric plasma to Europa's surface through a multi-fluid MHD model
Abstract
Europa's space environment is controlled by the wobbling of Jupiter's magnetic field, the magnetic response to this wobbling induced in the conducting subsurface ocean, and the interaction of Jupiter's magnetosphere with Europa's ionosphere and extended exosphere. We have developed a multi-fluid MHD model for Europa's plasma interaction which self-consistently solves for the bulk properties of 3 ion fluids and the electromagnetic fields in the vicinity of the moon. To validate our model, we have simulated the Galileo E4 Flyby using the observed plasma and magnetic field conditions. Our model has accurately reproduced Galileo magnetometer observations along the flyby trajectory, and provides full 3D density and velocity fields for O^+ and O_2^+ ionized from Europa's neutral O_2 exosphere, and the thermal, corotating O^+ from Jupiter's magnetosphere. Based on the three-ion-fluid MHD model, we have mapped the distribution of the magnetospheric plasma that was able to penetrate the plasma interaction to reach Europa's surface. We find that while the majority of downward flux impinges on the upstream hemisphere, the surface impact by the ambient magnetospheric O^+ ions exhibits a slight preference towards the anti-jovian hemisphere due to the influence of the convectional electric field. Under the E4 flyby conditions, we estimate that about 13% of the available upstream O^+ ions precipitate to Europa's surface. Most of the ambient plasma is instead diverted around the moon due to the plasma interaction with the ionosphere. This precipitation represents the contribution of thermal plasma to the sputtering interaction with Europa's icy surface which replenishes the O_2 exosphere.
- Publication:
-
42nd COSPAR Scientific Assembly
- Pub Date:
- July 2018
- Bibcode:
- 2018cosp...42E1383H