Simulation of the runaway electron beam formed in a discharge in air at atmospheric pressure

A numerical model is proposed which allows one to describe the dynamics of the fast electrons injected from the head of an anode-directed streamer. The model is based on solving numerically 3-dimensional equations of motion of electrons. In the context of the model, the number of electrons which can be injected from the surface of a streamer is determined by the number of electrons in the Debye layer. Results of numerical calculations show that about 10 of the electrons in the Debye layer are switched to the mode of continuous acceleration. The electrons that have not switched to the runaway mode form a residual space charge cloud, whose dimensions are several centimeters, near a streamer. The space charge screens the streamer tip; therefore, the generation of the runaway electron beam does not resume.