Dynamik und Kinetik schmaler Staubringe
Final Report Abstract
The major goal of the project has been a theoretical modeling of the central ringlet covering the orbit of the ring-moon Pan in the Encke division of the A ring of Saturn. The main idea has been that a population of small moonlets – moving co-orbital with Pan in horseshoe- and tadpole orbits – are assumed to act as sources to sustain the central ringlet. The model predicts a steady state ringlet which is able to explain the observed asymmetry of the ringlet owing to the action of plasma-drag, forcing the dusty motes to move in modified horseshoe orbits. Unfortunately, the optical depth of the model ringlet remains by far too small. Also direct collisions among the source moonlets, and related shaken off debris, cannot solve this discrepancy! As a way out we propose to check whether Pan itself can act as an efficient source provided that impact-ejecta is assisted by plasma-drag, so that the ejecta can enter the region of the central ringlet. Related studies are scheduled in the near future. Additionally, faint arcs were successfully modeled embracing the tiny moons Anthe and Methone observed by the Cassini-cameras. They have been found to be the result of a dynamical interplay of Mimas’ gravity at an outer corotation resonance with plasma interactions. There, particles generated by impact-ejecta processes at the moon’s surface are forced to librate around the central point of the corotation resonance, while they slowly leave this libration region driven by plasma drag/-sputtering. In this way a steady state arc is generated which matches the geometry of the observation. In the near future it is planned to perform photometric studies of the model arcs, so that these results can be directly compared with brightness (I/F) ISS-data in the images. With this approach we see a possibility to narrow down the poorly known parameters of the impact-ejecta process.
Publications
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Dust in the arcs of Methone and Anthe. October 2015
K.-L Sun, M. Seiß, and F. Spahn
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Particle dynamics in the central ringlet of Saturn’s Encke gap. October 2015
K.-L Sun, J. Schmidt, and F. Spahn
