Europa’s interaction with the Jovian magnetosphere: insights from the Galileo flybys

Europa, the smallest of the Galilean moons, is embedded within Jupiter’s magnetosphere where a rapidly flowing plasma interacts electromagnetically with the moon’s atmosphere and its surface. The magnetic field in the plasma is also affected by Europa’s induced magnetic field in a subsurface conducting layer. Between 1996 and 2000, the Galileo spacecraft executed eight close flybys of Europa for which magnetic field measurements were obtained. Since then, several numerical magnetohydrodynamic (MHD) models have been developed to examine the interaction between the rapidly flowing Jovian magnetospheric plasma and Europa and its atmosphere (e.g. Kabin et al. [1999], Schilling et al. [2007], Rubin et al. [2015], Harris et al. [2021]).

In this study, we investigate the large scale interaction of Jupiter’s magnetospheric plasma with Europa and its atmosphere with a single fluid MHD model. We apply the 3D multiphysics model ZEUS-MP, based on Duling et al. [2014], and also employed by Blöcker at al. [2016] to describe Europa’s interaction. Our model accounts for ion-neutral collisions, electron impact ionization, dissociative recombination, and electromagnetic induction in a subsurface water ocean. In particular, we prescribe Europa’s molecular oxygen atmosphere with a number of analytical models in which we consider several degrees of asymmetry of the atmosphere and the location of Europa along its orbit around Jupiter, and we constrain its composition with Hubble Space Telescope (HST) spectral images.

The resulting magnetic field is compared with measurements performed by the Galileo magnetometer. We present an analysis of the observations from the Galileo flybys taking into consideration the variable geometry of the trajectories. Our comparative study is used to further constrain properties of the moon’s atmosphere and to quantify the effects of their variability on the plasma interaction.