雷活動で観測される高エネルギー放射線とその発生メカニズム

Generation mechanism of high energy radiation observed during thunderstorm activity

鳥居 建男  

Torii, Tatsuo

冬の日本海沿岸で発生する冬季雷の活動時に環境放射線レベルが上昇する事象が観測されることがある。これまでの測定の結果、数10秒程度の緩やかな低エネルギーの放射線レベルの上昇と、その直後に発生する高エネルギー放射線による急峻な上昇という異なる2種類の放射線が観測された。本稿では、冬季雷活動時の放射線変動の観測結果を中心に、放射線が引き金となって発生すると考えられる雷放電の逃走絶縁破壊について概説する。

In recent years, increases of -rays seemed to be caused by thunderstorm activities have been observed during winter thunderstorms in Japan. Intense radiation during thunderstorms observed so far can be classified into two types. One is an instantaneous radiation burst lasts for no more than a few milliseconds, it is seemed that the bursts are produced in the process of lightning discharge. The other is the gradual fluctuations, last for a few to several tens of seconds, which are considered to be caused in a region of intense electric field within the thundercloud. In addition to the observed results during winter thunderstorms, the runaway breakdown thought to be triggering by the high energy radiation is outlined.