Spitale, J. and Porco, C.C. (2006). "Shapes and Kinematics of Eccentric Features in Saturn's C Ring and Cassini Division." American Astronomical Society, DDA meeting #37, #7.02.
Using high-resolution movies and azimuthal imaging scans with radial scales as fine as a few km and longitudinal resolutions as fine as a fraction of a degree, we examine the shapes and kinematics of a number of noncircular features in Saturn's rings.|
In the C ring, the Maxwell ringlet, at 1.45 Rs, is consistent with a freely-precessing Keplerian ellipse whose inner and outer edge apses are aligned. The 1.470-Rs ringlet shows about 5 km of scatter about a mean semimajor axis, but no coherent pattern is discernible. The 1.495-Rs ringlet shows residuals of about 5 km about a mean semimajor axis, but appears more complicated than a freely-precessing ellipse.
The B-ring outer edge shows the expected two-lobed shape rotating with the mean motion of Mimas, but with periapse leading the satellite by about 28 deg. That m=2 solution yields high residuals, which might be explained by a three-lobed pattern rotating at about 505.5 deg/day. In addition to the dominant m=1 eccentric, freely-precessing elliptical mode, the multi-mode Huygens ringlet also shows an m=2 shape with a pattern speed equal to, and phase almost exactly opposite to, that of the B-ring outer edge, suggesting that it is influenced not only by Mimas, but perhaps also by the outer B-ring. There may also be an m=6 mode precessing at about 631 deg/day.