Electron acceleration in a nonlinear shock model with applications to supernova remnants

Abstract

Monte Carlo calculations are presented of ion and electron spectraproduced by Fermi acceleration in a steady state plane parallel modifiedshock for Mach numbers of 170 and 43. The simulation assumes isotropicelastic scattering in the local fluid frame, consistent with resultsfrom plasma simulations. The shock structure is calculated taking intoaccount the back pressure of accelerated ions, and includesself-consistent pickup and acceleration of thermal ions. Results aredescribed for two dependences of scattering mean free path on rigidity.It is shown that these shocks are extremely efficient, with up to 98percent of the entering energy flux emerging as relativistic ions.Electron spectra are steeper than ion spectra at virtually all energiesrelevant for radio emission from SN remnants (0.3-30 GeV) and areslightly concave upward.