Stochastic flights of propellers

Abstract

Kilometer-sized moonlets in Saturn's A ring create S-shaped wakes called "propellers" in surrounding material. The Cassini spacecraft has tracked the motions of propellers for several years and finds that they deviate from Keplerian orbits having constant semimajor axes. The inferred orbital migration is known to switch sign. We show using a statistical test that the time series of orbital longitudes of the propeller Blériot is consistent with that of a time-integrated Gaussian random walk. That is, Blériot's observed migration pattern is consistent with being stochastic. We further show, using a combination of analytic estimates and collisional N-body simulations, that stochastic migration of the right magnitude to explain the Cassini observations can be driven by encounters with ring particles 10-20 m in radius. That the local ring mass is concentrated in decameter-sized particles is supported on independent grounds by occultation analyses.

10 pages, 7 figures, 1 table; accepted to MNRAS. v2: edited for mathematical and expositional clarity and completeness

References in corpus (5)

• Brownian Motion in Planetary Migration
• Care and feeding of frogs
• Stochastic orbital migration of small bodies in Saturn's rings
• Protoplanet Dynamics in a Shear-Dominated Disk
• Stochastic flights of propellers

Cited by in corpus (5)

• Migration of small moons in Saturn's rings
• Stochastic flights of propellers
• Incomplete cooling down of Saturn's A ring at solar equinox: Implication for seasonal thermal inertia and internal structure of ring particles
• A Librational Model for the Propeller Blériot in the Saturnian Ring System
• Hydrodynamic Simulations of Asymmetric Propeller Structures in Saturn's Rings