Inducing Fields and Lorentz force driven flows in the subsurface oceans of icy moons

Because of Jupiter’s rotation and the orbital motion of the Galilean moons, the subsurface oceans experience a time varying magnetic field. This gives rise to magnetic induction of electric currents, and the measurement of the related magnetic fields lead to the discovery of the subsurface oceans. The complex orbital motions yield magnetic field variations of different frequencies, with different amplitudes and phases that both change over time. Analyzing the orbital evolution, we provide a catalogue of these important parameters, which are crucial for interpreting the measured induced magnetic fields.

The interaction of the electric currents with the magnetic field results in Lorentz forces, which drive flows in the oceans. We perform numerical simulations of this process and identify two types of induced flows: 1) persistent axisymmetric westward flows and 2) flows reminiscent of inertial modes, which are typical for the dynamics of rotating systems. An attempt to scale our simulations to the ocean properties suggests that the flow amplitudes remain much slower than convective driven flows.