The Wave Mechanism of “Fast Breakdown” in Compact Intracloud Discharges

We propose a wave mechanism for explaining “fast breakdown” in thunderstorm clouds and the generation of powerful pulses of electromagnetic radiation of very high frequencies (VHF, from 30 to 300 MHz). A polarization wave moves along the discharge gap; an area of increased electric field is formed at the wave front, inducing the transition of corona micro-discharges into streamers. The mechanism does not require an electron-initiating source to start streamers, as in the case of direct avalanche-streamer transitions. It is assumed that the concentration of corona micro-discharges before the front is much greater than that of the streamers, since the threshold number of lengths of the electron avalanche growth for the ignition of the corona discharge is much smaller than that to start the streamer. The mechanism makes it possible to reduce the field strength necessary to initiate micro-discharges before the wave front. The wave is a self-consistent process of the birth of streamers, polarization of the medium, and the motion of the amplified-field area. It is a macroscopic analog of the ionization wave in a streamer: the elementary acts of ionization of molecules correspond to the emerging of streamers, such that the wave velocity ismuch greater than the speed of moving particles. For this reason, to denote a wave of fast breakdown, we introduce the term “streamerization,” which briefly and accurately reveals the essence of the process. The emerging streamers are sources of radio-frequency radiation. Calculations have shown the possibility of the front traveling at a speed of fast breakdown.