31st Annual Meeting of the DPS, October 1999
Session 40. Dust
Contributed Oral Parallel Session, Thursday, October 14, 1999, 8:30-9:40am, Sala Kursaal

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[40.05] The Fingerprint of the Magnetosphere on the Jovian Rings

M. Hor\'anyi (LASP)

New Galileo images (Ockert-Bell et al. Icarus 138, 188, 1999) and ground based observations (de Pater et al. Icarus 138, 214, 1999) confirmed that the continuous bombardment of the small moons is the source mechanism of dust particles in the ring/halo region and the gossamer rings of Jupiter (Burns et al. Science 284, 1146, 1999). The dynamics of these ejected grains is intimately related to the evolution of their spatial distribution and the appearance of the rings.

The most frequently cited dynamical model of the rings is based on slow transport (~105 years for a micron sized grain) due to Poynting-Robertson (PR) drag. In this model, resonance forcing due to the higher moments of the magnetic field (Lorentz resonances) are thought to explain the 3D structure of the rings (Burns et al. Science 284, 1146, 1999). This model captures the gross features of the rings, but it fails to explain several of the details shown by the new observations. For example:\newline 1. Thebe is indicated as a source of dust both inward and outward its orbit. Under PR drag particles are transported inward only.\newline 2. There is no hint yet in the data of sharp jumps in the vertical extent of the rings at the location of the Lorentz resonances or anywhere else.\newline 3. The main ring shows significant azimuthal brightness variations that should have been `sheared' away if the life time of the particles is long. Due to the very low optical depth in this region, self-gravity or collisions are unlikely to be responsible for these features.

In this talk we show, that the model of the ring/halo region based on very rapid transport (< few years) due to plasma gradients (Horányi and Cravens, Nature 381, 293, 1996) can be extended to the gossamer ring region providing solutions to the outstanding questions and an excellent fit to the observations. We argue that the observed spatial distribution of the dust is the result of the variations of the plasma parameters in Jupiter's magnetosphere.

The author(s) of this abstract have provided an email address for comments about the abstract: Mihaly.Horanyi@lasp.colorado.edu

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