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D.P. Hamilton (U. Maryland), H. Kr\"uger (MPIK, Germany)
Galileo dust data indicate that a significant population of particles in the 0.3 to 30 micron size range orbits Jupiter at distances from 10RJ to 100RJ; Pioneers 10 and 11 and Ulysses also detected large dust grains near Jupiter. Interpretation of these data is complicated by the fact that there are several possible sources of dust in the near-Jupiter region. One or more of the following sources may contribute significantly to the flux of dust in the 10RJ-100RJ region: i) gravitationally focused interplanetary and interstellar dust, ii) dust evolving outward from Jupiter's gossamer ring or Io, iii) electromagnetically trapped interplanetary and interstellar dust (Colwell and Horanyi 1996, Colwell et. al. 1998), iv) impact ejecta from the Galilean satellites, and v) impact ejecta from the outer eight satellites of Jupiter.
We are systematically investigating each of these possible sources, beginning with the Galilean satellite source which appears promising. A significant amount of material does escape from the Galilean satellites, as indicated by Galileo's detection of dusty ejecta during flybys of the Galilean satellites (Krüger et. al. 1999). Escaping ejecta will go into orbit around Jupiter, where it is strongly perturbed by satellite gravity, Jupiter's oblateness, and non-gravitational effects (principally radiation pressure and the Lorentz force). We have performed a set of numerical simulations including all of these effects. We find that gravitational interactions scatter dust to latitudes of 5 to 10 degrees producing a thickened disk of dust which encompasses Galileo's orbit and extending particle lifetimes against collision with the satellites to more than 500 years. A secular resonance due to non-gravitational forces pumps orbital eccentricities to 0.3-0.9, thereby allowing particles smaller than 15\mum to completely fill the region from 10RJ-50RJ. Furthermore, particles on high eccentricity orbits can strike satellites at speeds in excess of 10km/s, causing collisions energetic enough to produce additional ejecta.
DPH is grateful to NASA for supporting this research project.
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