Jupiter's internal structure and dynamics inferred from a high resolution magnetic field and secular variation model

The interior of Jupiter can be described broadly as a dense core surrounded by fluids, dominantly hydrogen and helium. The hydrogen rich metallic fluid generates the strongest planetary magnetic field in the Solar System. Modelling and interpreting this field give essential information about the dynamo process inside Jupiter. However, the depth of the dynamo region and the temporal variation of the magnetic field are still debatable. Here we use the Juno mission data across four years to derive an internal magnetic field model using spherical harmonic functions. We take the fluxgate magnetometer measurements acquired during the first 28 perijoves to compute a main field model to degree 13, and a secular variation model to degree 8. The power spectrum of the main field model is used to investigate the radius of the dynamo region. We use the properties of the non-zonal and quadrupole family spectra to infer that the convective region has an upper boundary at 0.843 ± 0.015 Jupiter radius. The slope of the secular variation timescales indicate that the dynamo is dominated by advective effects. The secular variation (SV) displays a maximum near the equator with a dipole structure in agreement with zonal drift of the Great Blue Spot. However, numerous small scale SV structures at mid and high latitudes suggest that the flow at the interior is complex involving both zonal and non-zonal features.