A self-consistent model of radial transport in the magnetodisks of gas giants including interhemispheric asymmetries

The magnetospheres of gas giants are characterised by their strong magnetic fields, the fast rotation of the planet and the presence of embedded active moons (Io at Jupiter, Enceladus at Saturn), releasing neutral gas and, from there, plasma in the innermost regions of the systems. Their dynamics is believed to be controlled by a balance between the centrifugal force acting on cororating plasmas trapped in the planetary magnetic field, plasma pressure gradients and magnetic forces. This balance determines the rate of outward transport of mass, angular momentum and energy and has a strong influence on the global configuration and dynamics of the magnetospheres. It results in the formation of a magnetodisk of plasma at the planetary equator, and a global outward transport of plasma from the innermost source regions to the outer magnetosphere where it is lost through magnetospheric boundaries or downtail. 
    Until now, description of this transport has followed two different approaches in the literature. “Corotation enforcement” models focus on the description of angular momentum transport in a disk exchanging momentum with the planetary thermosphere/ionosphere via electric current systems transferring magnetic torques. They assume mass and conservation but do not explicitly describe the transport processes through the magnetodisk. On the contrary, radial diffusion models do not explicitly take into account angular momentum transport nor exchanges between the planet and the magnetospheric plasma, but they describe radial transport of mass and energy assuming a certain state of turbulence in the magnetodisk.
    We present a unifying approach of the radial transport of mass, angular momentum and energy, using turbulent diffusion and including sources and sinks of plasma of arbitrary radial distribution throughout the disk. Our set of coupled equations independently describes momentum exchange with the two conjugate ionospheres, thus allowing for the study of interhemispheric asymmetries, such as the ones revealed by Juno, in this coupling. We will present solutions of our coupled set of transport equations that explore the different possible causes and effects of interhemispheric asymmetries in magnetodisk/planet coupling, with emphasis on the cases of latitudinally thin and thick disks corresponding respectively to the cases of Jupiter and Saturn. We will compare the outputs of our models with recent observational constraints brought by the Juno and Cassini missions.