Hedman, M.M., Burns, J.A., Tiscareno, M.S., Nicholson, P.D., and Porco, C.C. (2008). "Cassini Observations of Lindblad Resonances in Low Optical Depth Rings." American Astronomical Society, DDA meeting #39, #16.06.


Abstract
Images from the Cassini spacecraft reveal several unexpected structures in Saturn's faint rings that appear to be generated by Lindblad resonances. The clearest example of such a feature consists of a series of brightness in the outer part of the diffuse G ring that appear to be generated by the 8:7 Inner Lindblad Resonance with Saturn's moon Mimas (These features are located 170,000 km from Saturn center, and are distinct from the bright arc in the G ring located at 167,500 km). Similar but more complex structures are found in both the D ring (the innermost part of the ring system at 65,000-74,500 km from Saturn center) and the Roche Division between the A and F rings (137,000-140,000 km from Saturn center). The locations, pattern speeds and symmetry properties of the brightness variations in the D ring are consistent with 2:1 Inner Lindblad resonances, while those in the Roche Division appear to be caused by 3:4 Outer Lindblad Resonances. At both locations, multiple perturbations with periods ranging between 10.5 and 10.9 hours appear to be affecting the ring material. This overlaps the span of periods associated with Saturn's winds and magnetosphere, so these structures may be created by anomalies in Saturn's gravitational and/or magnetic fields. The relative strength and persistence of these patterns may therefore provide information about the structure of the planet's interior or the dynamics of the inner magnetosphere. Furthermore, all of these structures should provide new insights into how resonant perturbations affect disks of material in the regime where the disk optical depth is low and the typical particle size is small (1- 100 microns).