MODEL OF CURRENT FORMATION AT THE INITIAL STAGE OF THE RETURN STROKE OF SPARK DISCHARGE

The experimental studies of the break-through phase of the leader spark discharge in 1.3 m gap are presented. A numerical model is developed that describes the parameters of streamer zone and evolution of leader current during the break-through phase. The dependence of the leader velocity in the break-through phase on the magnitude of the reduced electric field E/N in the streamer zone is obtained. These dependences are compared with the measurement data; it is shown that the leader velocity V_L ∼ (E/N)^3/2. The agreement between the calculated and meas-ured time profiles of the leader current pulses in the breakthrough phase was obtained. It is shown that the main reason for the sharp increase in current at times of 1–2 µs is the increase in the reduced electric field in the streamer zone, associated with a decrease in the length of this zone as a result of the convergence of the leader heads. The field growth leads to an increase in the streamer velocity in the streamer zone, an increase in the leader current and the leader velocity.

return stroke of lightning discharge, leader channel, streamer zone of spark discharge, break-through phase of long spark