Observation of high energy radiation in winter thunderstorms

Torii, Tatsuo  ; Sugita, Takeshi*; Muraki, Yasushi*

The dose rate of the -rays increases in association with the activities of the winter thunderstorm. To investigate the time profile of the radiations during the winter thunderstorms, four sets of the radiation detectors were prepared which consist of the long proportional counters. Those results were compared with the results measured at the same time by the environmental radiation monitors set up around a nuclear power facility. Electric field was also measured by using a field mill. As a result, the following two types of the radiation enhancements have been found during the winter thunderstorm activities; the gradual variation of photon intensity with energy of a few MeV, and the burst type of the radiation that is attributed to the injection of high energy photons with the energy over 10MeV.