Short-Time Increases in the Gamma Ray Intensity and Electron Flux inside Thunderclouds As Studied at the High-Altitude Detector Point of the Tien-Shan Mountain Station

The events of short-time intensity increases in hard radiation in thunderclouds (thunderstorm ground enhancements, TGE) were studied at the Tien Shan mountain station (TSMS) of the Lebedev Physical Institute (LPI). Measurements of (30–3000) keV gamma rays and electrons accelerated to a few MeV are performed during close thundercloud passages using gamma and charged particle detectors placed at a height of 3750 m a.s.l. at the high altitude detector point of the station. The energy spectra of gamma rays associated with electric processes in the atmosphere are measured at the maxima of TGE events immediately in the spatial region of radiation generation inside thunderclouds. In some cases, a peak near ~500 keV is observed in the differential energy spectra of gamma rays, which can be interpreted as an annihilation line of the positrons generated in cascade processes of particles acceleration in thundercloud.