Precursor Waves in Shock Tubes

Abstract

Weymann's observation of a wave of electrons propagating from a strong shock into the region ahead of it is considered. By taking into account the mutual electrostatic repulsion of the electrons through a simple approximation, the main features of the precursor wave motion can be explained. In particular, the theory predicts the relatively gradual decrease in electron density from the shock to the electrostatic front, followed by exponential decay upstream from the electrostatic front.