Physics
Scientific paper
Dec 2005
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005agufm.p31d..03c&link_type=abstract
American Geophysical Union, Fall Meeting 2005, abstract #P31D-03
Physics
5759 Rings And Dust, 6265 Planetary Rings, 6275 Saturn
Scientific paper
The Cassini Ultraviolet Imaging Spectrograph observed eight stellar occultations by Saturn's rings with its High Speed Photometer between October, 2004, and August, 2005. Some occultations sampled the rings at two longitudes providing 11 radial profiles for portions of the rings. The radial separation of samples in the ring plane was as small as 7 m, with typical effective resolutions of ~20-40 m set by diffraction. Some ring edges are observed to be abrupt at these small scales, suggesting that simple fluid models fail to capture the particle dynamics. The transparency of the A ring varies by up to a factor of two between occultations due to the degree of alignment of gravitational wakes with the line of sight to the occulted star. These results are consistent with numerical simulations by Salo et al. (2004). Excess variance in the observed star signal indicates an auto-correllation due to clumps or particles with a size scale of several meters, reaching a peak in the middle of the A ring. Density waves and bending waves excited at locations of resonances with nearby moons have been measured with high resolution providing new constraints on the mass of the ring system. Second-order Janus waves in the Cassini Division and A ring and the Atlas 5:4 wave in the Cassini Division have been measured. The surface mass density of the A ring drops significantly beyond the Encke Gap. The auto-correlation length also drops in the outer A ring, but not as abruptly as the surface mass density. This suggests that particle sizes are not signficantly different, but that there is reduced gravitational clumping in the outer A ring. The effect of gravitational wakes does not show a strong radial dependence in the A ring, though azimuthal coverage is limited. The nine occultation profiles of the F ring show multiple components and azimuthal variability.
Colwell Joshua E.
Esposito W. L. W. L.
Miodrag Sremčević
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