1. Comet Shoemaker-Levy 9 and its Dust. 2. Resonant Trapping in a Self-Gravitating Planetesimal Disk

Details 1. Comet Shoemaker-Levy 9 and its Dust. 2. Resonant Trapping in a Self-Gravitating Planetesimal Disk 1. Comet Shoemaker-Levy 9 and its Dust. 2. Resonant Trapping in a Self-Gravitating Planetesimal Disk

Jun 1997

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1997phdt.........1h&link_type=abstract

Thesis (PHD). UNIVERSITY OF NOTRE DAME , Source DAI-B 57/12, p. 7570, Jun 1997, 127 pages.

Computer Science

1

Scientific paper

(1) Comet Shoemaker-Levy 9 (S-L 9) was imaged with the Hubble Space Telescope from January 1994 until impacting Jupiter six months later. Initial studies of the S-L 9 dust tail orientations have led some investigators to conclude the S-L 9 fragments were inactive. However surface brightness profiles of fragments G1, H, K, L, and S comae suggest the opposite. When observed far from Jupiter, these fragments' tailward profiles varied as ~rho-1 and their azimuthally averaged profile asymptotically varied as ρ-3/2, where ρ is the projected distance from a coma photocenter. Such profiles were consistent with active comet fragments having dust comae perturbed by radiation pressure. Simulations of an active comet are fitted to the observations and the fragments' dust grain size and outflow velocity distributions are extracted. It is shown that the appearance of the S-L 9 dust comae were dominated by large 10 μ m ~< R ~< 3 mm grains ejected at velocities ~1 m/sec. The fragments themselves were not detected directly; upper limits on their radii range from 1.0 to 1.5 km. However their dust mass loss rates of ˙ M~ 20 kg/sec place a lower limit of Rf ~> 0.4 km on their radii at the time of breakup. (2) The effects of collective particle behavior on the trapping strength of a perturber's mth order outer Lindblad resonance in a planetesimal disk are examined. It is shown that if the particle disk supports density waves, the spiral disk potential generated in response to forcing by the perturber shields particles from the perturber. This may diminish the perturber's ability to trap particles undergoing aerodynamic orbital decay. Density waves can transport away from resonance much of the angular momentum deposited in the disk by the perturber. If these waves are modestly damped by gas drag, particle collisions, and∨ downstream nonlinear effects, the angular momentum delivered to the particles is greatly reduced and cannot compensate their losses suffered due to drag. Hence wave propagation, when combined with a moderate degree of wave damping, weakens the perturber's trapping barrier. The range of disk conditions for which waves in the planetesimal disk inhibit particle trapping are described.

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