JOVIAN SYSTEM DATA ANALYSIS PROGRAM PROPOSAL SUMMARY

A Comparative Study of the Galileo-era Io Torus and Atmosphere PI: N. M. Schneider (CU/LASP) Co-I:s: F. Bagenal, F.J. Crary, A.I.F. Stewart (CU/LASP) One of Galileos prime mission objectives was to advance our understanding of the Io plasma torus. To this end, two UV spectrometers and a suite of fields-and-particles instruments were chosen for its study, and the imaging system joined in the study of Ios atmosphere. While the results of the individual instruments have been impressive, there has been little time to compare them with each other or with the current understanding of the Jupiter-Io system built from twenty-five years of work. We propose to undertake this type of comparative study, motivivated by the following goals: * Goal 1: Characterize the properties of the Io plasma torus during the Galileo prime mission - along with their spatial and temporal variations - and compare with previous remote and in situ observations. * Goal 2: Investigate the optical emissions generated by the interaction of Ios tenuous atmosphere with the jovian magnetosphere, with emphasis on morphology, excitation mechanisms, and comparison with previous observations. * Goal 3: Identify the processes that control the source, transport and loss of mass and energy from their origin in Ios atmosphere through the Io plasma torus. These broad scientific goals will be achieved through three specific tasks: * Task 1: Modeling Galileo UVS/EUV torus emissions. We propose to assist the Galileo UVS/EUV team by providing sophisticated models of Io torus emissions which test competing theories for torus structure and energetics. * Task 2: Velocity distributions from PLS torus data. We propose to expand on the work of the Galileo PLS team by performing a detailed analysis of particle energy distributions which are tracers for energy transport processes. * Task 3 - Analysis of SSI images of Ios atmosphere. We propose to undertake an independent analysis of SSI images of atmospheric emissions from Io while in eclipse by Jupiter. These three tasks are closely interrelated, and offer an opportunity to substantially improve our understanding of Ios atmosphere, the plasma torus and the processes which link them together.