A study published in Geophysical Research Letters investigates the magnetic signature of ocean circulation in Ganymede’s subsurface ocean using kinematic induction modeling.
The research couples zonal jet flows from rotating thermal convection simulations with magnetic field models that include Ganymede’s internal dynamo and external contributions from Jupiter.
Key Findings
The induction equation was solved in spherical geometry for deep-ocean (493 km) and shallow-ocean (287 km) scenarios with varying magnetic Reynolds numbers. Ocean flows generate a predominantly toroidal magnetic field through the omega-effect, with a weaker poloidal component extending beyond the conductive ocean layer.
For some induction configurations, analysis of time-averaged Lowes-Mauersberger spectra shows ocean-induced signals dominate at specific spherical harmonic degrees. Deep ocean scenarios with magnetic Reynolds numbers above unity produce surface magnetic signals up to 9 nT.
Implications
The results indicate that Ganymede’s intrinsic magnetic field creates favorable conditions for detecting subsurface ocean dynamics. The authors emphasize the need for low-altitude orbits for the Juice probe to detect these signals.
"Ocean flows generate a predominantly toroidal magnetic field through the omega-effect, with a weaker poloidal component extending beyond the conductive ocean layer."