Simulation Studies of Plasma Transport at Earth, Jupiter and Saturn

Abstract

In this chapter we present a review of plasma transport in the magnetospheres of the rapidly rotating outer planets Jupiter and Saturn with emphasis on the effects of magnetic reconnection. Unlike the Earth’s magnetosphere where reconnection is the dominant transport mechanism, atmospherically driven corotation dominates at Jupiter and Saturn. However, there is both observational and theoretical basis for reconnection at the outer planets. Since observations at the outer planets are sparse we have used numerical simulations to give an overall view of transport. For northward IMF, reconnection can erode the dayside Jovian magnetopause position by as much as 10 % while the simulations at Saturn indicate very little erosion. In the magnetotail, reconnection at Jupiter can become quasi-periodic in both Jupiter and Saturn simulations. There is observational evidence for this at Jupiter but the observational evidence is not as clear at Saturn. Solar wind dynamic pressure controls whether or not periodic reconnection occurs at Saturn while both dynamic pressure and the IMF are important at Jupiter. Both outflow-driven reconnection in which flux tubes reconnect as they convect from the dayside to the tail and solar-wind-driven reconnection are found in the simulations. One simulation study indicates that a pulse of increased dynamic pressure can trigger reconnection at Saturn. Large scale plasmoids do not remove enough plasma from the magnetospheres of either outer planet to account for loss of plasma from the inner magnetosphere sources. There is evidence in the Saturn simulations of Kelvin–Helmholtz waves driving transport.