The Dependence of Saturn's Magnetosphere and Polar Ionosphere on Solar Wind Dynamic Pressure and IMF Direction

The configuration and dynamics of the Earth's magnetosphere are largely controlled by the solar wind while Jupiter's magnetosphere is dominated by its massive rotating equatorial current sheet and plasma source at Io. Saturn has a rapid rotation equivalent to Jupiter but its magnetic field strength is comparable to that of the Earth. Thus Saturn is often called the planet whose characteristics are a mixture of those at Jupiter and the Earth. In a recent simulation study of the configuration of Saturn's magnetosphere for no interplanetary magnetic field (IMF), southward IMF and northward IMF we found that the Kronian magnetosphere always has vortices and turbulent convection which result from the interaction between the solar wind, corotation and magnetospheric convection. However the detailed configuration of the energy flux and field aligned currents (FACs) in the polar region are a function of IMF direction. In particular, the simulation results indicate that the vorticity causes intense FACs which are strongest near dawn. These results suggest that the Kronian magnetosphere can be quite different from both Jovian and terrestrial magnetospheres. In this study we have examined the effects of solar wind dynamic pressure and IMF BY component on Saturn's magnetosphere. We found that high dynamic pressures did little to change the Kronian convection for northward IMF while for no/southward IMF the convection patterns in the magnetosphere were changed as compared to the recent our study. The magnitudes of the energy flux and FACs are enhanced but the distributions are not changed. For the cases including IMF By component, the configurations of the magnetosphere and polar ionosphere are a mixture of those with no IMF and northward IMF. In this talk we will present these simulation results in detail and discuss the relation of the magnetospheric dynamics (in particular the convection) to the polar dynamics.