Spitale, J.N., Porco, C. C. (2011). "Forced and Free Distortions in Saturn's Huygens Ringlet" American Astronomical Society, DDA meeting #42 #8.05.


Abstract
Saturn's Huygens ringlet, located 250 km exterior to the outer edge of Saturn's B ring, has for some time been known to be eccentric; Porco (1983) measured a radial amplitude of 30 km using Voyager data sets, and based on the relatively large residuals in the simple Keplerian ellipse model, hypothesized that an additional wavenumber-2 pattern may be present as a response to the nearby Mimas 2:1 inner Lindblad resonance and/or the large-amplitude distortion in the massive B-ring edge, which at that time was assumed to be produced by the resonance. An attempt to fit such a pattern using 13 Voyager measurements (11 ISS images, one RSS occultation, and one UVS occultation) did not produce a statistically significant result. Using Cassini ISS imaging data, we show that the ringlet is indeed influenced by the Mimas resonance, and that there is an additional contribution from a free wavenumber-2 mode in the ringlet. The amplitudes of these modes, about 1 km each, are far too small to have been detected by Voyager.