Signatures of Enceladus in Saturn's E ring

Abstract

Dust production from Enceladus has long been suggested as the main source of dust in Saturn's E ring. This was supported by the observation that the ring's optical depth peaks close to the orbit of this moon. However, both HST and Keck observations indicated that the peak of the optical depth distribution in fact lies outside the orbit of Enceladus, with a displacement of approximately 104 km. Though this outward shift has been suspected to be a result of electromagnetic forces, it could not be reproduced in earlier studies. Here we show that it is intimately related to the initial inclinations of the grains produced in the recently discovered plumes. For grains with radii rg > 0.5 μm, the small initial inclination greatly reduces their re-collision probability, allowing for sufficiently long lifetimes for plasma drag to transport them outwards. Our numerical results can also be used in the simultaneous interpretation of the measurements by the Cassini CDA, RPWS instruments and imaging. Copyright 2007 by the American Geophysical Union.