Transverse electric discharges in supersonic air flows: Space-time structure and current-voltage characteristics of discharge

The space-time evolution of potential distribution in a pulsed transverse discharge in a supersonic jet of air is studied in a mode close to the current generator mode. The current dependences of the longitudinal electric field intensity and of the discharge channel diameter are measured for different values of pressure in the jet. It is demonstrated that the electric field intensity decreases with increasing discharge current by the power law, with the exponent being close to that for a highly contracted glow or arc discharge in the absence of flow. The increase in current is accompanied first of all by an increase in the discharge channel cross section. The characteristics of the oscillatory mode of discharge burning are studied for discharge power supplies which are close to the current generator mode. The obtained dependences of the oscillation period on the external parameters of discharge, namely, current, pressure, and interelectrode spacing, are interpreted. An expression is derived which describes the maximal extent of discharge along the flow in the case of instability due to external electric circuit. This extent may increase further only in the case of transition to supplies close to current generators; in this case, the extent is restricted by the mechanism of repeated breakdown.