Abstract
During a winter thunderstorm on 24 November 2017, a strong burst of gamma rays with energies up to was detected coincident with a lightning discharge, by scintillation detectors installed at the Kashiwazaki-Kariwa Nuclear Power Station at sea level in Japan. The burst had a subsecond duration, which is suggestive of photoneutron production. The leading part of the burst was resolved into four intense gamma-ray bunches, each coincident with a low-frequency radio pulse. These bunches were separated by 0.7–1.5 ms, with a duration of each. Thus, the present burst may be considered as a “downward” terrestrial gamma-ray flash (TGF), which is analogous to upgoing TGFs observed from space. Although the scintillation detectors were heavily saturated by these bunches, the total dose associated with them was successfully measured by ionization chambers, employed by nine monitoring posts surrounding the power plant. From this information and Monte Carlo simulations, the present downward TGF is suggested to have taken place at an altitude of , involving avalanche electrons with energies above 1 MeV. This number is comparable to those in upgoing TGFs.
- Received 5 March 2019
- Revised 19 May 2019
DOI:https://doi.org/10.1103/PhysRevLett.123.061103
© 2019 American Physical Society