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GEOPHYSICAL RESEARCH LETTERS, VOL. 33, L07201, doi:10.1029/2005GL025163, 2006

Self-gravity wakes in Saturn's A ring measured by stellar occultations from Cassini

J. E. Colwell

Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, Colorado, USA


L. W. Esposito

Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, Colorado, USA


M. Sremčević

Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, Colorado, USA


Abstract

An azimuthal brightness asymmetry in Saturn's A ring is caused by ephemeral agglomerations that continually form under the mutual gravity of the ring particles only to be torn apart by Keplerian shear. We calculate the shape and spacing of the self-gravity wakes from Cassini stellar occultations. The wakes are highly flatttened structures, with height/width ratio of 0.15 to 0.37, increasing outward across the A ring. The spacing between wakes increases with their height from a low value in the inner A ring of less than the wake width to >3 times the wake width in the outer third of the ring. The opacity of gaps between wakes also increases in the outer part of the ring where the wakes appear to be less coherent than in the inner and middle A ring. We calculate the vertical opacity of the A ring is 15–35% higher than previously reported.

Received 8 November 2005; accepted 17 February 2006; published 1 April 2006.

Index Terms: 6265 Planetary Sciences: Solar System Objects: Planetary rings; 5759 Planetary Sciences: Fluid Planets: Rings and dust; 6275 Planetary Sciences: Solar System Objects: Saturn; 6280 Planetary Sciences: Solar System Objects: Saturnian satellites.

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Citation: Colwell, J. E., L. W. Esposito, and M. Sremčević (2006), Self-gravity wakes in Saturn's A ring measured by stellar occultations from Cassini, Geophys. Res. Lett., 33, L07201, doi:10.1029/2005GL025163.