Collaborative research groups such as the University of Tokyo and Kyoto University have succeeded in simultaneously observing two types of radiation bursts caused by winter thunder activity at multiple high schools in Kanazawa City, Ishikawa Prefecture, which has become a precursor to the occurrence of thunder. Showed the possibility.In addition, Nagoya University, Kobe Municipal College of Technology, Kinki University, Hokkaido University, Kanazawa University, Toyama University, Shizuoka Prefectural University, Tokyo Metropolitan University, high schools, companies, institutions, local governments, etc. participated in the research group. There is.
Until now, the "trigger for the occurrence of lightning" has not been clarified for lightning activity.In recent years, the role of radiation has attracted attention, and since 2006, the research group has been promoting ground-based observations of radiation phenomena associated with winter lightning in Niigata and Ishikawa prefectures. In 2007, we succeeded in observing the "long burst", a phenomenon of weak radiation emitted from thunderclouds for several minutes, and showed that electrons accelerate to near the speed of light in thunderclouds. In 2017, we observed a short and strong radiation burst of less than 1 second that occurred at the same time as the lightning discharge, and elucidated the nuclear reaction of the lightning discharge in the atmosphere.However, the interrelationship between long bursts and short bursts with different durations and the effect on lightning discharge have not been clarified.
In the research, on January 2018, 1, a weak long burst emitted from a thundercloud passing over Kanazawa City, Ishikawa Prefecture for about 10 minute was observed.Furthermore, after a lightning discharge occurred during the observation and the long burst disappeared, a bright short burst of less than 1 second derived from the nuclear reaction was observed.From this observation, it was pointed out that the long burst may have promoted the occurrence of the short burst and the lightning discharge itself.
The research team is centered on young researchers.Focusing on winter lightning along the coast of the Sea of Japan, which is rare in the world, we are developing an observation network in cooperation with high schools and companies in Ishikawa Prefecture, and it is said that it will be expanded in the future.
Paper information:[Communications Physics] Gamma-ray Glow preceding Downward Terrestrial Gamma-ray Flash