JOVIAN SYSTEM DATA ANALYSIS PROGRAM PROPOSAL SUMMARY

Jupiter's magnetosphere, that region of space in which the planetary magnetic field is confined by the solar wind, is the largest of any planet in the solar system. It is also the most effective at accelerating charged particles to high energies. The magnetosphere therefore provides a unique laboratory for studying this and other phenomena that occur in many similar astrophysical systems. A principal goal of the Galileo orbiter was to collect the necessary data and this has been largely accomplished. We propose to study the dynamics of energetic ions in Jupiter's magnetosphere using data from the Heavy Ion Counter (HIC) and Energetic Particle Detector (EPD) on Galileo. These data will be organized under a framework based on the nonlinear dynamics applicable to particle motion in and around the plasma disk surrounding Jupiter. Interpreting the data in this way will produce new information on ion acceleration, transport, and loss processes. As a result of the depression in the planetary magnetic field by currents flowing in the plasma sheet, the ion motion there may be either regular or chaotic. These two basic types of motion allow substantially different access to remote areas of the magnetosphere, so that distinguishing between them is critical for proper data interpretation. We illustrate numerically calculated ion trajectories of each type and describe how we will extend such calculations with realistic magnetic field models as a basis for classifying the particle data. Data reduction techniques for achieving this result include calculations of particle composition, anisotropies, energy spectra, and phase space density gradients. Having established a basic description of the ion dynamics, we will be in a position to apply it to transport issues. The magnetosphere of Jupiter is known to be an efficient particle accelerator, but the mechanisms have not been well established. Our data analysis will allow us to determine the source locations, and thus the acceleration regions of the ions, which may be either steady or erratic. It will also determine transport coefficients and constrain the ionic charge states -- important for estimating the energy input to the Jovian aurora and confirming the original source of the ions respectively.