A hypersonic interpretation of the development of the spark channel in gases

Abstract

A new mechanism for the development of the spark channel in gases is proposed, in which it is assumed that the shock wave, known to exist after the channel is complete (Freeman and Craggs 1969), actually develops while the channel is still in formation. The paraboloidal shock is thought to derive its power from the transfer of energy only from the electrons pre-heated in front of the developing channel by field concentration to the neutrals and ions behind it (detonation wave mechanism). Neutral gas in front of the channel is considered to be cold. Analytical expressions for the velocity and position of the detonation wave are derived, and experiments by the authors and by previous workers tend to confirm the mechanism for certain low-density gases. The `radiation overshoot' characteristic of shock transmission through some gases has been observed, suggesting that a shock indeed exists prior to completion of the spark channel.