Hedman, M.M., Burns, J.A., Tiscareno, M.S., Porco, C.C. (2007). "The Heliotropic Rings of Saturn." American Astronomical Society, DPS meeting #39, #10.09.

Several faint eccentric ringlets around Saturn share a very unusual dynamical property: they maintain a particular orientation relative to sun. This is remarkable because previously known eccentric features in the rings precess so the part of the ring closest to Saturn drifts around the planet over a period of months at a rate determined by Saturn's oblateness. The ringlets described here, by contrast, are consistently found tens of kilometers further away from Saturn near local noon than they are near midnight. Features demonstrating this "heliotropic" behavior include the Encke Gap ringlets and a ringlet in the outer rift of the Cassini Division. These ringlets all have photometric properties which indicate that they are composed primarily of small dust grains 1-100 microns across, so they are more strongly affected by non-gravitational forces than other ring particles. In particular, solar radiation pressure acting on these small particles can generate average orbital eccentricities and orientations consistent with the observed shapes of these features. However, there are variations in the magnitude of the radial displacements depending on the brightness and the location of the ringlet which suggest that other forces or interactions also play a role in shaping this ring material.