Shock wave in a long-air-gap leader discharge

We report the shock wave phenomenon in an air-gap leader discharge observed using an interferometer. The continuous temporal evolution of the shock wave and plasma channel is recorded and reproduced with a thermohydrodynamic model based on the measured current, providing a prediction of the pressure pulses of the shock wave. The weak shock wave propagates at nearly the speed of sound, and the simulation results for the shock wave front positions and the plasma channel radius are consistent with experimental measurements. Experimental observations and numerical comparisons show that continuous energy injection results in a temporary overpressure process in the plasma channel and generates the shock wave. The pressure at the shock front falls rapidly and decays with propagation of the wave. In the weak shock region, the pressure wave decays as P∝R−3/4. The wave propagation predicted using the thermohydrodynamic model is compared with propagations predicted using the Vlases and Jones models, and we find that a measurement of the shock wave propagation trajectory gives an estimate of the energy injected to the leader channel during a discharge.