How well can we separate magnetic field contributions at Ganymede?

Among the icy satellites, Ganymede is unique in likely harboring a subsurface ocean while also possessing an intrinsic magnetic field strong enough to generate its own magnetosphere. Magnetic field measurements offer the potential to constrain ocean properties through electromagnetic induction studies. However, this requires an accurate separation of the various magnetic field contributions in Ganymede's environment, as well as a reliable model of its intrinsic field.

Using magnetic field data from the Galileo and Juno flybys, we investigate the challenges and uncertainties associated with modeling and disentangling variable external magnetic field contributions. We assess uncertainties in estimating Jupiter's large-scale magnetospheric field during the flybys and examine limitations of current MHD models of Ganymede's magnetosphere and their impact on inversions of Ganymede's intrinsic magnetic field. Our results highlight significant uncertainties in the external field and magnetospheric modeling, leading to non-negligible ambiguities in inferred intrinsic field parameters and in the interpretation of future magnetic field observations with JUICE.