Interaction of Europa with Jovian Plasma Torus: Hybrid Simulations

Abstract:

We present results of simulation of the interaction of Europa with Jupiter's magnetospheric plasma compared to in situ observations of Galileo spacecraft. For simulations we use multi-species hybrid (kinetic ions and fluid electrons) three-dimensional model. We consider O++, S++ as the main constituents of the Jovian plasma torus at Europa while its neutral atmosphere is considered to be composed primarily of (neutral) O2 molecules. We consider ionization processes of the neutral O2 atmosphere which is then a source of dense population of pick-up ions at Europa. We calibrate the ionization coefficients according to the comparison between simulated ion densities and densities observed in situ. We examine global structure of the interaction. The plasma composed of pick-up ions represents an obstacle for the Jovian magnetic field resulting in the compression of the magnetic field lines which in return causes development of temperature anisotropies. We study examine the regions where the threshold of temperature anisotropy driven instabilities has been reached and conclude what type of waves is generated in different regions of the interaction. We also focus on the refiling processes of the small cavity formed in the plasma downstream the relative plasma flow between Europa and the magnetospheric plasma. We acquire high resolution simulated data along virtual trajectories of Galileo which allows us to directly compare simulation results to in situ observations.