COLLISIONAL SIMULATIONS OF PARTICLES IN A NARROW PLANETARY RING

In order to better understand the effect of collisions on short-term features in narrow planetary rings, we have developed a model to investigate how particle-particle collisions might modify some consequences of satellite perturbations. To mimic the effect of collisional scattering, we use a Monte Carlo-like simulation that alters the velocities of model ring particles in the same manner as collisions with actual particles might. In this way we can simulate collisions while tracking individual particles in our model. Using parameters (collision frequency, coefficient of restitution, and orbital elements of colliders) appropriate for the F ring in a two-dimensional numerical model that incorporates the collisional simulation as well as the perturbations of adjacent satellites, we can reproduce periodic features seen in the Voyager images. Not surprisingly, we find that collisions wash out periodic features within approximately a collisional relaxation time (the interval over which the random component of velocity introduced by collisions equals the systematic velocity introduced by the perturbers). The induced random velocity depends on both the amount of energy dissipation per collision and the collision frequency. Our simulation should not be applied to long-term phenomena because it is not self-consistent, in that the modeled ring particles do not transfer angular momentum back to the perturbing moons. © 1992.