Observation of energetic radiation associated with winter thunderstorm activity

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

-ray dose-rate increase associated with thunderstorm activities was observed on the ground in winter. To investigate the fluctuation profile during winter thunderstorms, the energetic radiation was measured by using four set of radiation detectors (LPRCs) which consist of four long proportional counters (2.5 m in length; 10 cm in diameter). These LPRC have a different response characteristic for the incident particle by mounting shield covers. It was also compared with the result measured at the same time by the environmental radiation monitors adopting an NaI scintillator / ionization chamber as a detector. Moreover, the electric field was measured at the same site by using a field mill. In the observation from December, 2006 to February, 2007, the count-rate fluctuation which seem to originate from thunderstorm activity observed by the LPRCs.