Hydrodynamic Model of Diffusion Effects on Shock Structure in a Plasma

Diffusion effects on the structure of a steady, plane shock in a proton-electron plasma have been studied using a simplified, two-fluid, hydrodynamic model in which diffusion is the only shock broadening mechanism. Charge separations occur inside the shock because of the mass difference between protons and electrons. The shock is shown to have electric field and density oscillations as a function of distance through the shock. The peak electric fields are large; the peak electric field inside a weak shock of Mach 1.169 reaches 41 700 v/cm for typical quiescent plasma conditions. The distance in which electric field changes occur is of the order of ten Debye lengths of the quiescent plasma. The present work is limited to shocks of Mach number less than 2.