Gamma Ray Flashes Produced by Lightning Observed at Ground Level by TETRA‐II

Abstract

In its first 2 years of operation, the ground-based Terrestrial gamma ray flash and Energetic Thunderstorm Rooftop Array (TETRA)-II array of gamma ray detectors has recorded 22 bursts of gamma rays of millisecond-scale duration associated with lightning. In this study, we present the TETRA-II observations detected at the three TETRA-II ground-level sites in Louisiana, Puerto Rico, and Panama together with the simultaneous radio frequency signals from the lightning data sets VAISALA Global Lightning Dataset, VAISALA National Lightning Detection Network, Earth Networks Total Lightning Network, and World Wide Lightning Location Network. The relative timing between the gamma ray events and the lightning activity is a key parameter for understanding the production mechanism(s) of the bursts. The gamma ray time profiles and their correlation with radio sferics suggest that the gamma ray events are initiated by lightning leader activity and are produced near the last stage of lightning leader channel development prior to the lightning return stroke.

A Satellite‐Detected Terrestrial Gamma Ray Flash Produced by a Cloud‐to‐Ground Lightning Leader

“…For the first question, previous studies have reported downward TGFs observed at the ground level associated with both natural and triggered CGs. In natural CG cases, downward gamma rays have been linked with downward stepping negative leaders (Abbasi et al, 2018; Pleshinger et al, 2019) but this type of X‐ray/gamma ray generation from leader steps is at least 2 to 4 orders of magnitude weaker in fluence than satellite‐observed TGFs and appears to be a distinct phenomenon.…”

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

“…Therefore, the cases of Abbasi et al (2018) are still 10 −6 to 10 −4 times smaller than the present case. The ground-based experiment TETRA-I/II also reported 46 downward TGFs in total during summer as well (Pleshinger et al, 2019;Ringuette et al, 2013). Gamma-ray counts of TETRA-II BGO (25.4 × 2.5 × 2.5 cm 3 ) range from 19 to 203.…”

“…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.…”

Synchrotron mechanism of X-ray and gamma-ray emissions in lightning and spark discharges

“…Recent observations have shown that gamma radiation correlates with radio-frequency radiation and is generated at the last stage of lightning leader channel development prior to the lightning return stroke [14]. The bursts of 30-80 MHz radiation because of leader stepping were observed in [15].…”