Electrostatic Conditions That Produce Fast Breakdown in Thunderstorms.

Fast breakdown (FB), a breakdown process composed of systems of high‐velocity streamers, has been observed to precede lightning leader formation and play a critical role in lightning initiation. Vigorous FB events are responsible for the most powerful natural radio emissions on Earth, known as narrow bipolar events (NBEs). In this paper, an improved version of the Griffiths and Phelps (1976, https://doi.org/10.1029/jc081i021p03671) model of streamer breakdown is used alongside supervised machine learning techniques to probe the required electric fields and potentials inside thunderstorms to produce FB and NBEs. Our results show that the electrostatic conditions needed to produce +FB observed in New Mexico at 9 km altitude and −FB in Florida at 14 km altitude are about the same, each requiring about 100 MV potential difference to propagate 500 m. Additionally, the model illustrates how electric field enhancement ahead of propagating FB can initiate rebounding FB of the opposite polarity. Key Points: An electrostatic model for fast breakdown in thunderstorms is proposed and used to explain features of narrow bipolar event waveformsPositive and negative polarity breakdown requires about the same 100 MV potential difference available in New Mexico and Florida stormsFast breakdown can be bidirectional with electric fields ahead of a streamer system creating rebounding opposite polarity breakdown [ABSTRACT FROM AUTHOR]