Influence of the internally induced magnetic field on the plasma interaction of Europa

Abstract

In this paper, we study the influence of electromagnetic induction in Europa's interior on the plasma interaction in the vicinity of Europa. We describe the temporally periodic interaction between Europa and the Jovian magnetosphere with a three‐dimensional time‐dependent model. Our model describes simultaneously the three‐dimensional plasma interaction of Europa's atmosphere with Jupiter's magnetosphere and the electromagnetic induction in a subsurface conducting layer due to time‐varying magnetic fields and plasmas including their mutual feedbacks. We find that the induced magnetic fields cause time varying asymmetries in the current density and the plasma density outside Europa. We show that the Alfvén current system is deformed and displaced because of the induced magnetic fields. Furthermore, the plasma wake of Europa is deformed because of the induction. Remarkably, therefore the influence of the induced fields on the Alfvén wings and the plasma wake may be seen at distances where the induced fields are already negligible. The effects of induction on the wake structure are most clearly visible in the E4 flyby magnetic field and plasma observations, which are in good agreement with our simulation. The resulting structure of Europa's plasma wake could explain why Galileo measurements did not detect high plasma densities along the E4 trajectory.