Local Time Asymmetries in Saturn's Magnetosphere

The role of Saturn's rotation in powering its magnetosphere is well known. However, there is intense debate on whether the solar wind driven convection plays a substantial role in Saturn's magnetospheric dynamics. In Jupiter's magnetosphere, it has been shown that major local time asymmetries exist in the middle and inner magnetosphere suggesting that solar wind plays a substantial role in redistributing plasma in the magnetosphere, determining the plasma sheet thickness and reconnection geometry in the outer magnetosphere. Cassini has now provided a comprehensive local-time coverage of Saturn's magnetosphere. However, determining current densities in Saturn's magnetosphere from magnetic field measurements is fraught with difficulties. The chief amongst them is the fact that because of a lack of a dipole tilt and therefore a lack of a current sheet tilt, Cassini does not rapidly cross the current systems in Saturn's magnetosphere, making it difficult to distinguish between temporal and spatial gradients. Another, difficulty arises from cyclical perturbations imposed by rotating plasma and magnetic field asymmetries in the magnetosphere which complicates averaging and differencing of the magnetic field required to calculate the current density in the magnetosphere. In this presentation, after summarizing the basic physics governing the magnetospheric dynamics (internal and external sources of plasma, momentum, dynamics and reconnection), I will present new results summarizing local time asymmetries (with a special focus on the dawn-dusk asymmetries) of the current sheet thickness, asymmetries of the height integrated azimuthal and radial electric currents and field-aligned current intensities in Saturn's magnetosphere. I will introduce heuristic models to explain how these asymmetries are generated and discuss how quantitative models can be constructed to account for them.