Towards an understanding of the morphology of Jupiter’s magnetic field

As has been recognized since the completion of Juno’s first nine orbits, Jupiter’s magnetic field is morphologically distinct from that of the other planets. Six years later, with over 50 additional orbits, that picture has not fundamentally changed. While, like Earth, the field has a strong axial dipole component, the most intense field occurs in two distinct regions: the Great Blue Spot (GBS) and the Northern Hemisphere Flux Band (NHFB). Elsewhere, there are large regions of very low flux. What processes drive this field morphology?  While the axial dipole is almost certainly the result of a global dynamo (though of uncertain depth extent), these other features likely result from more localized dynamical processes. We consider various possibilities to explain the GBS, including flux expulsion, but only concentration of flux by a convergent (i.e. downwelling) flow seems plausible. For the NHFB, enhanced convection at the outer edge of the tangent cylinder to a deep stably stratified region is one possibility, though this does not explain the lack of such a feature in the southern hemisphere. Here, too, flux concentration by convergent flow is also a possibility. The regions of low flux may indicate the regions from which flux has been swept by divergent flow towards the regions of convergent flow. We will also discuss whether such processes are consistent with predominantly zonal flow in the presence of possible stable stratification.