Morphology of the imprints of spark current channels in a point–plane gap in air

Using the autograph (imprint) method, the imprint microstructure of current channels that are associated with a submicrosecond spark initiated in air in a point–plane gap with the point charged both negatively and positively has been studied. For both polarities of the point, the imprints of the current channels 0.2–0.5 mm in size on the surface of the flat electrode represent areas that contain morphological modifications in the form of microcraters 0.3–5.0 $\mu$m across and tracks. The surface concentration of the microcraters equals (2–5) $\times$ 10$^4$ mm$^{-2}$. It has been found that the microcraters are arranged on the tracks, which produces an intricate net structure. The internal submicron microstructure of the microcraters and tracks has been discovered.