Libration and migration of propeller moons in Saturns dense rings

• Applicant: Professor Dr. Frank Spahn, Ph.D.
• Subject Area: Astrophysics and Astronomy
• Term: from 2014 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 252107923

One of the most interesting findings of the Cassini-mission has been a Non-Keplerian excess motion of the largest propeller moonlets. Studies in the first project phase have indicated that these longitudinal librations might be excited by near-resonant perturbations caused by the numerous Saturnian satellites, while ring-moonlet interactions have the potential to amplify the libration amplitude, as suggested by our linearized moonlet-propeller model. In the continuation phase we plan to complete our numerical modeling of the resonantly driven moonlet-libration by incorporating dissipative effects mimicking the numerous irreversible moonlet-ring interactions (physical collisions, gravitational scattering). With this approach stationary libration properties can be expected and their dependence on the dissipation rate could help to identify dominating librations. The amplification of these certain libration amplitudes - demonstrated by the linearized moonlet-propeller oscillator for a single mode in the previous project phase - will now be modeled by hydrodynamic simulations of a moonlet freely moving in a dense granular ring-fluid. This approach will permit us to capture the non-linear character of the moonlet-propeller interactions, which may allow the excitement and amplification of multiple (interacting) libration modes. Further, we will compare the related results with the current Cassini imaging data.

• DFG Programme: Research Grants
• Co-Investigator: Dr. Martin Seiß