Observation of an energetic radiation burst from mountain-top thunderclouds

Tsuchiya, Harufumi*; Enoto, Teruaki*; Torii, Tatsuo; Nakazawa, Kazuhiro*; Yuasa, Takayuki*; Torii, Shunsuke*; Fukuyama, Taro*; Yamaguchi, Takahiro*; Kato, Hiroshi*; Okano, Shinji*; et al.

Physical Review Letters, 102(25), p.255003_1 - 255003_4, 2009/06

https://doi.org/10.1103/PhysRevLett.102.255003

During thunderstorms on 2008 September 20, a simultaneous detection of -rays and electrons was made at a mountain observatory in Japan located 2770 m above sea level. Both emissions, lasting 90 seconds, were associated with thunderclouds rather than lightning. The photon spectrum, extending to 10 MeV, can be interpreted as consisting of bremsstrahlung -rays arriving from a source which is 60-130 m in distance at 90% confidence level. The observed electrons are likely to be dominated by a primary population escaping from an acceleration region in the clouds.