Study in a source of radiation from the thundercloud which makes environment radiation fluctuate

2014 Fiscal Year Final Research Report

• Project/Area Number: 24360399
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Partial Multi-year Fund
• Section: 一般
• Research Field: Nuclear engineering
• Research Institution: Japan Atomic Energy Agency
• Principal Investigator: TORII Tatsuo 独立行政法人日本原子力研究開発機構, 福島研究開発部門 福島環境安全センター, 特任参与 (20421795)
• Co-Investigator(Kenkyū-buntansha): KAMOGAWA Masashi 東京学芸大学, 教育学部, 准教授 (00329111) ; IGUCHI Tetsuo 名古屋大学, 工学(系)研究科(研究院), 教授 (60134483)
• Project Period (FY): 2012-04-01 – 2015-03-31
• Keywords: 雷雲 / 逃走絶縁破壊 / 制動放射線 / 宇宙線 / ラドン子孫核種

Outline of Final Research Achievements

Intensive and transient energetic radiations associated with winter thunderstorm activities were detected around the coast of Sea of Japan. We identified the source location of the transient energetic radiation, lasting for several minutes, through the observations of radiation, atmospheric electric field, and radar echoes. Our identification indicated that the energetic radiation was emitted from a downward hemispherical surface with regardless of lightning discharge, the bottom of which was about 300 m above sea level. This may occurs due to the generation of bremsstrahlung photons caused by electric fields inside the thunderstorm, because the energy of the observed radiation exceeds that of the radiation emitted from natural nuclides.The photon flux largely increases just under the thundercloud if we assume that the electric field around the downward hemispherical surface is - 400 kV/m, and the photon energy spectrum shows a large increase in the energy region of several MeV.

Free Research Field

放射線計測