Multi-fluid MHD Modeling of Europa's Plasma Interaction

Abstract:

Europa hosts a periodically changing plasma interaction driven by the variations of Jupiter's magnetic field and magnetospheric plasma. We have developed a multi-fluid MHD model for the plasma interaction to investigate its response to these magnetic field and plasma variations at Europa's orbit. The model solves the multi-fluid MHD equations for electrons and three ion fluids (magnetospheric O⁺ as well as O⁺ and O₂⁺ originating from Europa's ionosphere) while incorporating sources and losses in the fluid equations due to ionization, electron heat conduction, charge exchange, recombination and other relevant collisional effects. Using input parameters constrained by the Galileo MAG and PLS observations, we first demonstrate the accuracy of our model's representation of the plasma interaction by simulating the Galileo E4 and E14 flybys, which took place under different upstream conditions and sampled different regions of Europa's interaction. Our model produces 3D magnetic field and plasma bulk parameters that agree with and provide context for the flyby observations. We next present the results of a parameter study of Europa's plasma interaction at three different System-III longitudes within Jupiter's magnetosphere, for three different global magnetospheric states, comprising 9 steady-state simulations in total. We describe how Europa's ionosphere is self-consistently generated in response to the external plasma conditions, and show how the relative strengths of the magnetospheric plasma versus Europa's ionosphere control Europa's global interaction with Jupiter's magnetosphere.