Model of the Streamer Zone of a Leader

Abstract:

Developed leaders represent highly conductive plasma channels, continuously emitting a fan of streamers, termed the streamer zone. The tip moves at a speed much slower than that of individual streamers. A huge number of short-lived streamers in the corona generate the space charge field required to maintain the streamer propagation. A critical issue is the conversion from the streamer to leader phase [Da Silva and Pasko, 2013]. The objective of this paper is to present simulations of the formation and propagation of the streamer zone of a leader. In these simulations we generated a group of streamers that propagate in a discharge gap while they interact with each other. We use the modified numerical model [Likhanskii et al., 2007] developed to simulate discharge plasma actuators driven by nanosecond pulses. The model uses 2D rectangular computational box, and the discharge gap is filled with the air at normal conditions. Furthermore the model considers electrons, positive and negative ions. The plasma kinetics and interaction with neutral molecules is modeled in a drift-diffusion approximation [Likhanskii et al., 2007]. The electric field and potential are related to the density of charged species according to the Poisson equation. The latter was solved by the successive over-relaxation method. It is shown that interaction between the streamers significantly reduces their propagation velocity. Furthermore the streamer velocity depends on the distance between the streamers. The smaller is that distance the stronger is the suppression of the streamer velocity. This explains why the leader, which consists of many streamers, is much slower than a single streamer formed in the same discharge gap.

C.L. Da Silva and V.P. Pasko, J. Geophys. Res.: Atmospheres, 118, 1-30, 2013 A.V. Likhanskii et al., Phys. Plasmas, 14, 073501, 2007.