Measurement of energetic radiation caused by thunderstorm activities by a sounding balloon and ground observation

放射能ゾンデ及び地上測定による雷活動を起因とする高エネルギー放射線観測

鳥居 建男  

Torii, Tatsuo

雷活動により高エネルギー放射線が様々なフィールドで観測されている。その放射源を調査するために、放射能ゾンデ, 航空機、及び地上観測により放射線の測定を行った。ゾンデ観測では2つのGM管を用いて雷活動中に放球した。その結果、雷雲中の高度57.5km付近で2桁程度の放射線計数率の上昇が観測された。さらに、冬季には日本海沿岸で地上観測を行い、高エネルギー放射線を観測した。これらの測定結果及び雷雲をモデル化したモンテカルロ計算結果との比較について報告する。

Energetic radiation caused by thunderstorm activity is observed at various places, such as the ground, high mountain areas, and artificial satellites. In order to investigate the radiation source and its energy distribution, we measured energetic radiation by a sounding balloon, and the ground observation. On the measurement inside/above the thundercloud, we conducted a sounding observation using a adiosonde mounted two GM tubes (for -rays, and for /-rays), in addition to meteorological instruments. The balloon passed through a region of strong echoes in a thundercloud shown by radar image, at which time an increase in counting rate of the GM tube about 2 orders of magnitude occurred at the altitude from 5 km to 7.5 km. Furthermore, the counting rate of two GM tubes indicated the tendency different depending on movement of a balloon. This result suggests that the ratio for the -rays (energetic photons) of the beta-rays (energetic electrons) varies according to the place in the thundercloud. Furthermore, we carried out a ground observation of the energetic rays during winter thunderstorm at a coastal area facing the Sea of Japan. Two types of the energetic radiation have been observed at this time. We report the outline of these measurements and analysis in the session of the AGU meeting.