The magnetospheres of gas giants are dominated by the presence near their centrifugal equator of a plasmasheet/magnetodisk filled with thermal plasmas originating from active moons: Io at Jupiter, Enceladus at Saturn. These plasmas are transported from their region of generation in the inner magnetosphere to the outer magnetosphere where they are lost through magnetospheric boundaries or downtail. Their transport 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. In turn, this balance determines the rate of outward transport of mass, angular momentum and energy in these plasmasheets and has a strong influence on the global configuration and dynamics of these magnetospheres.
Until now, description of this transport has followed two different lines 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 conservation but do not explicitly describe the transport of energy. On the contrary, radial diffusion models do not explicitly take into account angular momentum transport, but they describe radial transport of mass and energy assuming a certain state of turbulence in the plasmasheet.
We present a unifying approach of the radial transport of mass, angular momentum and energy, using turbulent diffusion acting on 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 in this coupling. We will show solutions of our coupled set of transport equations that explore the different possible causes and effects of interhemispheric asymmetries in plasmasheet/planet coupling, with emphasis on the cases of latitudinally thin and thick disks corresponding respectively to the magnetosheres of Jupiter and Saturn.