[M-IS24] Atmospheric electricity: High energy phenomena

[MIS24-P03] A simple altitude measurement of the electron accelerator for lightning gamma rays in the Kanazawa area during the winter of 2022.

*Tanaka Atsuya¹, Kazuhiro Nakazawa¹, Keigo Okuma¹, Yuki Omiya¹, Mii Ando¹, Manari Oguchi¹, Teruaki Enoto², Yuuki Wada³, Yuko Ikkatai⁴, Ting Wu⁵, Daohong Wang⁵ (1.NAGOYA UNIVERSITY, 2.Kyoto University, 3.Osaka University, 4.Kanazawa University, 5.Gifu University)

Keywords:gamma-rays from thunderstorm , Winter thunderstorm

Winter thunderclouds are observed from November to March every year along the Sea of Japan coast, and one of their characteristics is the MeV gamma-ray radiation observed on the ground. There are two types of thunderstorm gamma rays: terrestrial gamma ray flashes (TGF), which are emitted on a time scale of less than 1 ms associated with lightning discharges, and gamma-ray glows (Glow), which is emitted from the thunderclouds themselves on a time scale of a few minutes. The GROWTH experiment has been observing the Japan Sea coast in winter since 2006, and we, the Nagoya Univ. group joined the campaign from 2018..
In FY2022 season, we deployed our observation systems to two detector sheds in Kanazawa City. Both are equipped with large GOOSE (Gamma-ray Orientation Observing System with Electron-monitor) detectors. It consists of scintillator detectors with lead collimators and an electron detector. Its purpose is to measure the altitude of the electron acceleration region by directional observation of MeV gamma-rays and direct detection of MeV electrons from the acceleration region. Based on the observation results of the previous year (Okuma et al. 2022 JpGU), the thickness of the lead collimator was doubled to 5 cm this year in order to enhance the directivity. We also installed two new prototype detectors aiming at directional observation of TGFs (Ando et al, this meeting).
In four months of observations to date, a TGF and a Gamma-ray glow were detected on December 6. There were another TGF and Gamma-ray glow on December 18, and two TGFs on December 23. The rate of TGF detection is several times higher than ordinary. In this presentation, we will report the latest status of the observations, focusing on the event analysis of the two GOOSE instruments.