• Richardson, Derek C.
• Perrine, Randall P.

Abstract

We report on an ongoing study of planetary ring dynamics. We use local simulations to examine the effects of gravitational perturbations by a small moonlet on patches of ring material of scale 10<SUP>4-6</SUP> km<SUP>2</SUP>. We use the numerical code pkdgrav to model the motions of 10<SUP>5-7</SUP> ring particles as they interact by self-gravity and collisions, using a sliding patch model with periodic boundary conditions. Our boundary conditions include a randomization routine that erases perturbations by the moonlet when particles wrap azimuthally. We run this highly parallelizable code on local clusters and national supercomputers. <P />Our method allows us to explore a wide parameter space, including particle size distributions, particle density, surface friction, and coefficient of restitution; moonlet size, shape, density, rotation, eccentricity, and vertical oscillation; patch size, gap width, two or three-dimensional geometries, and ring surface density (i.e. optical depth). In addition, particle self-gravity and collisions can be turned off independently. We have only begun to explore this huge parameter space. <P />Our work thus far has been to further constrain the mass, density, and eccentricity of the moonlet Daphnis, located in the Keeler gap, by varying the moonlet mass and eccentricity, and (for the first time) using a realistic non-spherical shape model for the moonlet. We also aim to provide further constraints on the equilibrium spins states, and the collisional and surface properties (viscosity) of the ring particles, by varying the surface friction, density, and coefficient of restitution of the particles. Future improvements to the model include adding a cohesive strength model to study the effect of sticky particle aggregation on equilibrium ring properties. We report on results from our latest simulations and compare edge-wave formation with linear analytical theory. <P />This work is supported by a NASA Earth and Space Science Fellowship. <P />...

Topics

• density
• impedance spectroscopy
• surface
• cluster
• theory
• simulation
• strength
• viscosity