Title

Noncircular Features In Saturn'S Rings I: The Edge Of The B Ring

Keywords

Occultations; Planetary rings; Saturn, rings

Abstract

A comprehensive investigation of all available radio and stellar occultation data for the outer edge of Saturn's B ring, spanning the period 1980-2010, confirms that the m=2 distortion due to the strong Mimas 2:1 inner Lindblad resonance circulates slowly relative to Mimas in a prograde direction, with a frequency ΩL=0.1819°d-1. Our best-fitting model implies that the radial amplitude of this distortion ranges from a minimum of 3km to a maximum of 71km, with short-lived minima recurring every 5.42yrs. In addition to the dominant m=2 pattern, the edge of the B ring also exhibits at least four other perturbations. An m=1 component with a radial amplitude of ~20km rotates at a rate very close to the expected local apsidal precession rate of π{variant}̇B~5.059°d-1, while smaller perturbations are seen with m=3 (amplitude 12.5km), m=4 (5.9km), and m=5 (5.6km), each of which has a pattern speed consistent with that expected for a spontaneously-generated "normal mode" (French, R.G. et al. [1988]. Icarus 73, 349-378). Our results for m=1, m=2 and m=3 are compatible with those obtained by Spitale and Porco (Spitale, J.N., Porco, C.C. [2010]. Astron. J. 140, 1747-1757), which were based on Cassini imaging data. The pattern speed of each normal mode slightly exceeds that expected at the mean edge radius, supporting their conclusion that they may represent a series of free modes, each of which is trapped in a narrow region between the mode's resonant radius and the ring's edge. However, both our model and that of Spitale and Porco fail to provide complete descriptions of this surprisingly complex feature, with post-fit root-mean-square residuals of ~8km considerably exceeding typical measurement errors of 1km or less. © 2013 Elsevier Inc.

Publication Date

1-1-2014

Publication Title

Icarus

Volume

227

Number of Pages

152-175

Document Type

Article

Personal Identifier

scopus

DOI Link

https://doi.org/10.1016/j.icarus.2013.09.002

Socpus ID

84885706617 (Scopus)

Source API URL

https://api.elsevier.com/content/abstract/scopus_id/84885706617

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