Two types of energetic radiation observed in winter thunderstorms

冬季雷活動時に観測された2種類の高エネルギー放射線

鳥居 建男  ; 杉田 武志*; 村木 綏*

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

冬季雷活動時に観測される放射線挙動を明らかにするために、4基の比例計数管を用いて粒子,エネルギーの特徴を調査した。その結果、落雷前にエネルギーが13MeV程度の緩やかな上昇が観測され、続いて雷放電とほぼ同時にエネルギーが10MeV超の高エネルギー放射線バーストが観測された。

The dose rate of the -rays increases in association with the activities of the 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. These detectors have different characteristics of the response for the energy of the incident particles by mounting different thick shielding covers. 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 10 MeV.