Role of photoionization processes in propagation of cathode-directed streamer

The effect of the electron distribution in front of the cathode-directed streamer head on the characteristics of the discharge itself has been analyzed in this paper. Both the process of gas photoionization in front of the streamer head and the effect of spatially uniform `background' pre-ionization have been taken into consideration. It is shown that the substitution of the actual photoelectron distribution in front of the streamer head for uniform `background' pre-ionization makes it possible, by the variation of this parameter, to attain the coincidence of some characteristics of the streamer discharge (streamer velocity, conduction current, electron distribution in the streamer head and channel), not allowing for coincidence of all the characteristics simultaneously in this case. The analytical model that allows us, with the use of the known streamer head potential, to obtain associated values of the head radius and peak electric field strength has been proposed and verified.