Modeling the Interior Dynamics of Gas Planets

Wicht, J., French, M., Stellmach, S., Nettelmann, N., Gastine, T., Duarte, L. and Redmer, R.

Abstract

With NASA’s Juno mission having arrived at its target and ESA’s JUICE mission in planning, the interest in state-of-the-art models for the interior structure and dynamics of Jupiter is increasing. This chapter reports on the related attempts within the Special Priority Program PlanetMag of the German Science Foundation and provides an up-to-date review of the topic. Refined interior models are discussed that are based on new ab initio calculations for the equations of state for hydrogen and helium. For the first time, the depth-dependent transport properties have also been calculated, most notably an electrical conductivity profile that captures the transition from the molecular outer to the metallic inner hydrogen-rich envelopes. Anelastic simulations of convection show that the strong density stratification causes flow amplitudes to increase with radius while the flow scale decreases. Zonal jet systems very similar to those observed on Jupiter or Saturn are found in simulations of the molecular hydrogen envelope. Dynamo simulations that include the whole gaseous envelope show strikingly Jupiter-like magnetic field configurations when the strong density stratification is combined with an electrical conductivity profile that includes the significant drop in the molecular layer. While the dipole-dominated large-scale field is produced at depth, the equatorial jet can give rise to a secondary dynamo process where it reaches down to regions of sizable electrical conductivity. The magnetic surface signatures of this secondary dynamo are banded but also have more localized wave numberm=1 and m=2 concentrations at lower latitudes. By detecting these features, the Juno mission should be able to constrain the deep dynamics of the equatorial jet.