A PHASE-SPACE FLUID SIMULATION OF A 2-COMPONENT NARROW PLANETARY RING - PARTICLE-SIZE SEGREGATION, EDGE FORMATION, AND SPREADING RATES

A two-component kinetic equation is solved numerically for a flattened narrow planetary ring. The Krook kinetic equation for single-sized identical planetary ring particles (see. T. G. Brophy and L. W. Esposito (1989, Icarus 78, 181-205) or F. H. Shu and G. R. Stewart (1985, Icarus, 62, 360-383)) is generalized for the case of two-component systems. The generalized two-component equations are solved numerically using the phase-space fluid computational method developed in Brophy and Esposito (1989). The results of a simulation of a two-component narrow ring, in which the large particles are eight times as massive as the small particles, are presented in detail. The dynamics of the unconstrained edges of this ring are resolved by the simulation and show sharpening not expected for single-component rings. This is due to a tendency for small particles to accumulate at the edges of the ring, creating a flatter and sharper edged equivalent optical depth profile than that for a single-component ring. This is caused by a tendency for equipartition of random kinetic energies which retards the large particle evolution and quickens the small particle evolution, and by torques exerted by each component on the other at edges due to each component having a different asymmetric drift speed. The tendency for equipartition causes damping of the large particle dispersion velocity which results in a slower overall spreading rate for the ring than that for a single-component ring of similar equivalent optical depth. © 1990.