High-precision time study of gamma-ray bursts during thunderstorms

• Published in: Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment Accelerators, spectrometers, detectors and associated equipment, 2023-01, Vol.1045, p.167515, Article 167515
• Main Authors: Kuriyama, E., Masubuchi, M., Koshikawa, N., Iwashita, R., Omata, A., Kanda, T., Kataoka, J., Tsurumi, M., Diniz, G., Enoto, T., Wada, Y.
• Format: Article
• Language: English
• Subjects: Gamma-ray glows; Gamma-ray imaging; Lightning discharge; TGFs; Thunderstorm
• ISSN: 0168-9002; 1872-9576
• DOI: 10.1016/j.nima.2022.167515

Strong gamma-ray bursts initiated by lightning discharges and thunderclouds have been observed since the 1980s. However, the process of these emissions is under debate. Observed gamma-ray bursts are classified into two types according to their duration. One is a short-duration burst, called a terrestrial gamma-ray flash (TGF), and the other is a gamma-ray glow, which has a longer duration. The observation of a TGF is challenging because of its extremely brief duration (less than a second). As a result, the physics behind TGF is relatively poorly understood compared to classical long-duration bursts, the gamma-ray glows. To study short gamma-ray bursts, we developed a new detector system with time precision of 10 ns and focused on low-energy (E< 100 keV) measurement. We began our observations in November 2019 in a mountain area over 300 m above sea level and approximately 25 km from the Japan Sea. In this paper, we report the observations leading to the detection of the three types of interesting gamma-ray bursts, some of which were associated with lightning discharges. These results suggest the importance of measurements with high-time resolution and low-energy photons for understanding gamma-ray bursts related to thunderclouds. Moreover, we also report our first observation of gamma-ray imaging of a gamma-ray glow detected in the 2021–2022 season.