Particle Scattering in Astrophysical Environments

Abstract

Theoretical details behind the computation of accurate quantum mechanical cross sections are presented in this chapter. Partial wave scattering is discussed in detail with emphasis on collisions involving common astrophysical gases including hydrogen, helium, and oxygen. Details involving the computation of partial wave scattering are included. Ab initio interaction potentials for common astrophysical collisions are discussed along with empirical models utilized during computation. Comparisons between laboratory scattering parameters and theoretical parameters are shown with excellent agreement. For complicated atom-molecule or molecule-molecule collisions, an empirical scaling cross section theory was developed allowing for accurate energy-angular dependent cross sections for unknown collision species. The computational methods and algorithms used for particle transport are also discussed for both neutral and charged particles. Monte Carlo methods and random number generation is explained in detail and with generalization for any transport medium.Monte Carlo simulations for the interaction between solar wind ions and the upper atmosphere of Mars are discussed for several different solar conditions. Thermalization rates and non-thermal escape fluxes are shown and compared to simulations utilizing classical scattering models. Additionally, Monto Carlo simulations for the transport of helium ions through the interstellar medium are discussed. Hot helium spatial energy distributions within the heliosphere are shown using the local bubble boundary and the nearest collection of stars as sources for nascent hot helium ions. Details and implications for all simulation results are discussed.