冬季雷活動時における高エネルギー放射線挙動の観測

Observation of high energy radiation in winter thunderstorms

鳥居 建男  ; 杉田 武志*; 村木 綏*

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

冬季雷活動時に環境放射線モニタの線量率が上昇する事象が観測されることがある。この放射線の特徴を把握するために、異なる遮へい材を使用した比例計数管を用いて、冬季雷活動時に観測される高エネルギー放射線挙動について調査した。その結果、雷放電前に緩やかな上昇を示し、雷放電とほぼ同時に放射線バーストが発生する事象が観測された。前者のエネルギーは1-3MeV、後者は10MeV超であった。

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.