Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Torii, Tatsuo; Sugita, Takeshi*; Tanabe, Sachiko*; Kimura, Yoshihisa*; Kamogawa, Masashi*; Yajima, Kazuaki*; Yasuda, Hiroshi*
Taiki Denki Gakkai-Shi, 3(1), p.111 - 112, 2009/00
Fluctuations of energetic radiation that were seemed to be caused by a summer thunderstorm activity were observed at the top of Mt. Fuji. The largest of such fluctuations was gradual and lasted for about 20 minutes, and was found to be high-energy 
rays having a continuous energy spectrum up to 10 MeV or more. As for the feature of these fluctuations, it seems naturally that such fluctuations are caused by the bremsstrahlung photons generated by the runaway electrons produced continuously with an intense electric field in the thundercloud rather than originated in the process of lightning discharge.
Torii, Tatsuo; Sugita, Takeshi*
Taiki Denki Gakkai-Shi, 2(1), p.105 - 106, 2008/00
The influence of runaway electron generation by atmospheric radionuclides in a thunderstorm electric field is examined. The behavior of radiation emitted by radon, thoron and their decay products in the electric field was analyzed by Monte Carlo calculations. The results showed that a large amount of electron-ion pairs are produced in air when the electric field intensity exceeds 250 kV/m at the altitude of 2 km (about 320 kV/m at the sea-level equivalent pressure). Furthermore, the influence of the resuspension of fallout nuclides was analyzed because lightning activity after the Chernobyl nuclear accident increased in central Sweden where a considerable amount of nuclides fell. It is shown that, similar to natural radioactive nuclides, these nuclides significantly influence the ionization within the thundercloud.
Torii, Tatsuo; Sugita, Takeshi*; Muraki, Yasushi*
Taiki Denki Gakkai-Shi, 1(2), p.73 - 74, 2007/00
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.