Magnetic Field Induced by Convective Flow in Ganymede's Subsurface Ocean

Abstract It has been suggested that the convective flows in Ganymede's subsurface ocean can generate a magnetic field that is strong enough to be measured by future space missions. Here, we investigate this hypothesis by developing a numerical model of Ganymede's magnetic field induced by the motion of salt water in its interior. The model is based on solving the equation of electromagnetic induction for flow velocity fields obtained from the numerical simulations of rotating convection. To assess the sensitivity of the solution to the flow geometry and material parameters, we use different flow models and systematically explore the parameter space, with free parameters including the electrical conductivity of water and ice, the depth of the ocean and the thickness of the ice crust. Our results suggest that the strength of the flow induced magnetic field increases with the thickness and electrical conductivity of the ocean, ranging from 0.5 nT for km and S/m to 10 nT for km and S/m. The magnetic field is controlled by large‐scale toroidal flow in the ocean and its structure is sensitive to the latitudinal distribution of zonal jets. Although the magnetic field induced by ocean circulation is more than two orders of magnitude weaker than Ganymede's core magnetic field (GCF), it can be, in principle, extracted from the observed data because its spectrum decreases slower than the GCF spectrum.