Torrey, P.A., Tiscareno, M.S., Burns, J.A., and Porco, C.C. (2008). "Mapping Complexity: the Wavy Edges of the Encke and Keeler Gaps in Saturn's Rings." American Astronomical Society, DDA meeting #39, #15.19.


Abstract
The edges of the Keeler and Encke gaps of Saturn's A Ring are significantly disturbed as the embedded moons (Daphnis and Pan, respectively) interact with the adjacent dense rings. Cassini images of these edges reveal the structure to be much more complex than predicted by analytical perturbation theory (Tiscareno et al 2005, DPS). In the Encke Gap, we see both amplitude and frequency modulations of the expected monochromatic sinusoid, as well as some sharper 'glitches' in the pattern. In the Keeler Gap, the expected 32-lobed pattern in the inner edge due to a resonance with Prometheus is 'lumpy' and asymmetric, while the outer edge features sharp-edged asymmetric 'wisps'.

Much of the unexpected structure may be due to the superposition of multiple patterns, each moving with its own frequency. Determination of these pattern speeds will help us to identify the source of the perturbations, and may help us better appreciate the transfer of angular momentum between dense particle disks and embedded moons. We will present high-resolution maps of these edges covering all longitudes and at many points in time.