Close encounters in Coulomb and gravitational scattering. I - Relaxation of isotropic test-particle distributions by like-particle collisions

Abstract

view Abstract Citations (11) References (55) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Close Encounters in Coulomb and Gravitational Scattering. I. Relaxation of Isotropic Test-Particle Distributions by Like-Particle Collisions Shoub, Edward C. Abstract A procedure for solving the Boltzmann equation is developed and applied to the problem of describing the effects of close encounters in Coulomb and gravitational scattering. An initial-value problem is considered in which spatially homogeneous, isotropically distributed test particles relax to equilibrium by means of like-particle Coulomb collisions with a fixed Maxwellian background. The time evolution of the test particle's velocity distribution is calculated using the Boltzmann and Fokker-Planck collision terms, and the results are compared. Close encounters are shown to be unimportant, relative to the cumulative effects of distant encounters, for near-equilibrium initial conditions, but to very important for highly nonequilibrium initial conditions, leading to a view of the way in which energetic test particles thermalize that is qualitatively different from that derived from consideration of distant encounters alone. That identical-particle effects assume a new importance due to close encounters is noted. Contrary to accepted views, the Kolmogorov-Feller and Boltzmann collision terms are shown not to be equivalent for isotropic distribution. Publication: The Astrophysical Journal Pub Date: April 1992 DOI: 10.1086/171231 Bibcode: 1992ApJ...389..558S Keywords: Boltzmann Transport Equation; Celestial Mechanics; Coulomb Collisions; Fokker-Planck Equation; Isotropic Media; Particle Collisions; Boundary Value Problems; Energetic Particles; Gravitational Fields; Maxwell Equation; Astrophysics; CELESTIAL MECHANICS; STELLAR DYNAMICS; PLASMAS full text sources ADS |