JOVIAN SYSTEM DATA ANALYSIS PROGRAM PROPOSAL SUMMARY

Twenty-five years of observations in Jupiter's magnetosphere have produced a picture of a vast, complex and variable system. The plasmas and fields in Jupiter's magnetosphere are controlled by a combination of atmospherically driven corotation, the plasma source at Io and the solar wind. We are challenged to use the time series of observations along a spacecraft trajectory to assemble a picture of the configuration and dynamics of this entire system. In this proposal we present a plan to use a global magnetohydrodynamic simulation of the interaction of the solar wind with Jupiter's rapidly rotating magnetosphere to help tie the observations together into a self-consistent view of the entire system. A key difficulty in modeling the Jovian magnetosphere is the presence of widely different time scales between the inner and outer magnetosphere. If traditional explicit methods are used, unrealistically small time steps are necessary to resolve the short Alfven travel time close to Jupiter. The new simulation model described in this proposal for the first time will allow us to model the entire magnetospheric system including the inner magnetosphere and the Io source. Our new semi-implicit simulation code has been in development for the past 3 years. This is the first time this approach will be used to model a planetary magnetosphere. In our application of the code to Jupiter we will be guided by the observations. First we will concentrate on modeling the quasi-steady magnetosphere that results when the solar wind and IMF are held constant for extended periods of time. We also will investigate the effect of changes in the Io source. We will compare these results with statistical studies of the magnetic field and plasma flow. Then we will conduct studies of the temporal evolution of the system to try to understand the sometimes-dramatic changes observed in Jupiter's magnetosphere.