36th DPS Meeting, 8-12 November 2004
Session 7 Rings
Oral, Monday, November 8, 2004, 3:30-6:00pm, Lewis

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[7.12] Highly Inclined Orbits in Thebe's Gossamer Ring

D.P. Hamilton (U. Maryland), H. Krüger (MPI Aeronomie)

Each of the four small satellites orbiting near Jupiter is accompanied by a dusty ring of debris presumably lofted from these satellites by hypervelocity impacts of interplanetary micrometeoroids. The outermost and faintest of these rings, which is associated with the satellite Thebe, has an outward extension that we have previously argued is due to a shadow resonance (Hamilton 2003, DPS meeting #35, #11.09). This effect, caused by the abrupt shutoff of photoelectric charging when a dust particle enters Jupiter's shadow, results in coupled oscillations of the particle's orbital eccentricity and semimajor axis. Ring material spreads outward from Thebe while maintaining its vertical thickness just as observed by Galileo imaging.

The Galileo dust detector (DDS), which made two passes through this ring, revealed further mysteries, however. We observe that 1) particle fluxes drop immediately interior to Thebe's orbit, and 2) some detected particles have high inclination orbits. We have investigated and nearly ruled out the possibility that spurious events, such as impacts into the detector walls or the magnetometer boom, are masquerading as particles with high inclinations. Searching for a physical explanation, the findings appear to be consistent with grains being driven to large inclinations by a strong Lorentz resonance immediately interior to Thebe as argued by Hamilton et al. (1998, DPS meeting #30, #15.06). The grains would form a halo of material faint enough to be invisible to imaging, but populated enough to be detected by direct impacts onto the Galileo sensor. We will report on numerical simulations that include both the shadow resonance and the Lorentz resonance, and will assess the likelihood of this possibility by comparing DDS data to our numerical simulations.

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Bulletin of the American Astronomical Society, 36 #4
© 2004. The American Astronomical Soceity.