High Peak‐Current Lightning Discharges Associated With Downward Terrestrial Gamma‐Ray Flashes

Abstract

During 2017–2018 winter operation of the Gamma‐Ray Observation of Winter Thunderclouds experiment in Japan, two downward terrestrial gamma‐ray flashes (TGFs) that triggered atmospheric photonuclear reactions were detected. They took place during winter thunderstorms on 5 December 2017 and 9 January 2018 at Kanazawa, Ishikawa Prefecture, Japan. Each event coincided with an intracloud/intercloud discharge, which had a negative‐polarity peak current higher than 150 kA. Their radio waveforms in the low‐frequency band are categorized as a distinct lightning type called “energetic in‐cloud pulse” (EIP). Negative‐polarity EIPs have been previously suggested to be highly associated with downward TGFs, and the present observations provide evidence of the correlation between them for the first time. Furthermore, both of the downward TGFs followed “gamma‐ray glows,” minute‐lasting high‐energy emissions from thunderclouds. It is suggested that the negative EIPs took place with downward propagating negative leaders or upward positive ones developed in highly electrified regions responsible for the gamma‐ray glows.

Upward Negative Leaders in Positive Upward Lightning in Winter: Propagation Velocities, Electric Field Change Waveforms, and Triggering Mechanism

“…It is also different from return strokes in that there are only a few pulses lasting for ~200 μs before the main pulse, and no typical PB pulses can be identified. This special type of event has recently been reported by Wada et al (2020) to be associated with downward terrestrial gamma ray flashes. Two events reported by Wada et al (2020) had estimated peak currents of −260 and −197 kA.…”

“…This special type of event has recently been reported by Wada et al (2020) to be associated with downward terrestrial gamma ray flashes. Two events reported by Wada et al (2020) had estimated peak currents of −260 and −197 kA. Although we cannot estimate currents of the events we observed, the fact that these events saturated all of the observation sites indicates that they also carried extremely large current.…”

Meteorological Aspects of Gamma‐Ray Glows in Winter Thunderstorms

“…Event 7 was followed by a downward terrestrial gamma‐ray flash, as reported in Wada et al. (2020). The duration, the number of photons, and fitting parameters of the glow events are shown in supporting information (Wada et al., 2021).…”

Photonuclear Reactions in Lightning: 2. Comparison Between Observation and Simulation Model

“…In addition to satellite observations, TGFs have been observed by on-ground apparatus (Abbasi et al, 2018;Bowers et al, 2017;Dwyer et al, 2004Dwyer et al, , 2012Hare et al, 2016;Pleshinger et al, 2019;Ringuette et al, 2013;Tran et al, 2015;Wada et al, 2020). Observations of Bowers et al (2017), , , and (Wada et al, 2020) were performed in winter thunderstorms, and the others in summer ones. In the case of Bowers et al (2017), assuming photoneutron productions by the downward TGF, they concluded that 10 17 gamma rays were emitted.…”