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C.E. Chavez, C.D. Murray, K. Beurle, N. Cooper, M.W. Evans (QMUL), J.A. Burns (Cornell), C.C. Porco (SSI)
Images of Saturn's F ring region obtained by the Cassini ISS cameras have shown periodic structures ("gores") in azimuth. Some images also show a "streamer" connecting the inner part of the F-Ring with Prometheus, the inner shepherding satellite. The origin and short-term evolution of these features have been explored using a numerical model that includes Prometheus and 40,000 test particles; the system was followed for five orbital periods of Prometheus. The results show that the streamer and the gores are related to one another. As Prometheus enters the inner strands of the F ring and then retreats it causes local changes in semi-major axis and eccentricity that form the streamer. One orbital period later, the ring displays a gore with a radial gradient that is consistent with Keplerian shear. The streamers and gores are due to the localised changes in orbital elements due to the close encounter with Prometheus. The model provides excellent agreement with structures observed in the Cassini images and predicts more dramatic perturbations as the orbits of the F ring and Prometheus approach anti-alignment in late 2009.
This work is funded by PPARC and NASA. C.E.C. is grateful to the Mexican Council for Science and Technology CONACYT and the Astronomy Unit, Queen Mary, University of London for financial support.
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Bulletin of the American Astronomical Society, 37 #3
© 2004. The American Astronomical Soceity.