Plasma and gas-dynamic near-electrode processes in the initial phase of a microstructured spark discharge in air

The results of studies of the dynamics of near-electrode processes in the initial phase of a spark discharge in atmospheric-pressure air in the point-plane geometry are presented. After breakdown, regions of about 50 $\mu$m or more in size with an increased electron concentration of (3 – 8) $\times$ 10$^{19}$ cm$^{-3}$ near the surface of the flat cathode have been observed. With allowance for the experimental data on erosion effect of the discharge on the surface of a flat electrode and the associated gas-dynamic effects, a physical model of near-electrode processes has been proposed, based on which the gas-dynamic parameters are estimated.