On the Possible Threshold Character of the Spark Microstructure Formation

The influence of the limiting discharge current on the formation dynamics of spark channels in air at atmospheric pressure is studied. It is shown that the gap current limitation to several tens of amperes results in a sharp decrease in the growth rate of the spark channel from the cathode. At given current amplitudes, the channel microstructure is not resolved, and the maximal electron density of the observed plasma is ≈(1–2) × 10 19 cm –3 on the scale of ~100 μm in the near-cathode region.