Giant Planet Interior Dynamics in the Context of Rotating Turbulence Scaling Laws

All four giant planets in our solar system feature planetary-scale magnetic fields and internal heat fluxes that exceed the adiabat. These observations point towards vigorous convection inside the planets, while some stable stratified internal layers have also been suggested. Rotating convective scaling laws can be employed to infer the bulk characteristics of planetary interior dynamics. A recent theoretical study connected the turbulent convection scaling laws across nonrotating, slowly rotating, and rapidly rotating regimes (Aurnou et al. 2020).

Here we apply these scaling laws to the interior dynamics of the four giant planets in the solar system. With the measured heat flow as a critical input parameter, we estimate the characteristic flow speeds and dynamical length-scales within the different giant planet convective zones. These estimations inform us about the importance of rotation on the local dynamics via the local Rossby number. In addition, they can be used to kinematically evaluate the local magnetic field generation efficiency and the importance of Lorentz force via the local magnetic Reynolds number and the local Elsasser number. Our analysis indicates that the local magnetic Reynolds number exhibits a dichotomy between the gas giants and the ice giants. We will discuss how this might contribute to the dipole-multipole dichotomy in their observed magnetic fields.