Extensive Cloud Showers (ECS) – New High-Energy Phenomena Resulting from the Thunderstorm Atmospheres

We report the phenomenon of the Extensive Cloud Showers (ECS) detected by the surface particle detectors at mountain altitudes in correlation with thunderstorms. Measured microsecond duration particle bursts are first direct evidence of the electron-photon avalanches in the thunderstorm atmospheres, reaching the mountain altitudes from low located thunderclouds. In the report we present analysis of these rare events including spatial distribution, density spectra and particle energy.