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At present, it is impossible to explain the mechanism of lightning initiation in thunderclouds without considering the key role of powerful discharges that occur 0.04–3 ms after the lightning initiation. These discharges are termed Initial Breakdown Pulses (IBPs), and their peak currents are comparable to the high currents of lightning return strokes to the ground [Rakov & Uman, 2003].
In turn, it is impossible to explain such strong IBPs occurring within such a short timeframe (0.04–3 ms) without the initiating (triggering) role of secondary electrons, positrons, and photons from cosmic-ray Extensive Air Showers (EAS) with an initial particle energy above 10^15 eV [Kostinskiy et al., 2020a]. For effective lightning initiation, the flux of secondary electrons from an extensive air shower must increase exponentially within the strong electric fields of a thundercloud [Kostinskiy et al., 2020b].
Consequently, based on the analysis of the initial stages of lightning initiation and development, it can be stated with high probability that without extensive air showers, intracloud lightning and Narrow Bipolar Events (NBEs) would not occur at all.
Co-funded by the European Union (MERIT - Grant Agreement No.101081195).
Kostinskiy, A. Y., Marshall, T. C., & Stolzenburg, M. (2020a). The mechanism of the origin and development of lightning from initiating event to initial breakdown pulses (v.2). JGR:A, 125, e2020JD033191. https://doi.org/10.1029/2020JD033191
Kostinskiy, A.Y., Vlasov, A. and Fridman, M. (2020b). Calculation of the dynamics of the initiation of streamer flashes that provide the NBE VHF signal profile and the VHF phase wave propagation velocity. arXiv: 2005.12417 [v1] [physics.ao-ph] https://doi.org/10.48550/arXiv.2005.12417
Rakov, V. A., & Uman, M. A. (2003). Lightning: Physics and effects. Cambridge: Cambridge Univ. Press