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J. E. Colwell, M. Horanyi (LASP, University of Colorado)
Interplanetary dust particles entering the magnetospheres of the jovian planets move on orbits which are affected by radiation pressure and electromagnetic forces as well as gravity. As these particles traverse regions of the magnetosphere with rapidly varying plasma properties, they may exchange energy and angular momentum with the magnetosphere. Some small (~1 micron radius) grains may become trapped into long-lived orbits by this process. At Jupiter, interstellar as well as interplanetary grains can be captured. The capture leads to a diffuse population of particles on predominantly retrograde orbits, some of which have been detected by the Galileo DDS (Colwell et al., Science Vol. 280, pp. 88-91, 1998). The capture mechanism operates at Saturn as well, but a much smaller population of captured dust is expected. Relative velocities between interstellar dust and Saturn are higher than at Jupiter preventing capture of interstellar dust at Saturn. Captured dust is smaller at Saturn (0.15 micron radius) than at Jupiter (1 micron radius). In numerical simulations of captured dust trajectories, we find some particles at Saturn that are trapped in orbits at high magnetic latitudes and never cross the ring plane. At Jupiter, the captured dust occupies a toroidal region of space from the outermost edge of the main rings to about 20 jovian radii. We will describe the dynamics of captured exogenic dust at Jupiter and Saturn and the prospects for detecting this dust at Saturn with the Cassini Cosmic Dust Analyzer. This work is supported by NASA.