The growth of plasma convection in Saturn's inner magnetosphere

We report Rice Convection Model simulations of centrifugally driven plasma convection in Saturn's inner magnetosphere (2<L<12), incorporating a continuously active distributed plasma source. The distributed plasma source is a key element that distinguishes convection at Saturn, where the source is broadly distributed, from that at Jupiter, where the source is largely confined to the Io torus. At Saturn, the broadly distributed source produces fast, narrow inflow channels alternating with slower, wider outflow channels, consistent with Cassini Plasma Spectrometer observations. We have also investigated the relative roles of pickup currents and Coriolis acceleration in producing the magnetospheric corotation lag. Comparison with observed corotation lags indicates that the plasma source model adopted in earlier RCM simulations needs refinement. We will incorporate newer plasma source models [e.g., Smith et al., 2010] that imply much larger plasma mass loading rates and different radial distributions of charge exchange versus electron impact ionization rates. We expect that this modification will be partly compensated by increasing the assumed Pedersen conductance of Saturn's ionosphere, as also indicated by recent aeronomical calculations [Moore et al., 2010].