Abstract
Experimental work of the past few years has shown that runaway breakdown determines the maximum electric field strength in thunderclouds and is behind a variety of phenomena newly observed in thunderstorm atmosphere, such as TGFs, TLEs, etc. The necessary condition for the occurrence of runaway avalanche is the existence of high-energy electrons. In the atmosphere, these are the cosmic ray secondary electrons. Therefore the observed effects reflect close relationship between cosmic rays and electrodynamic processes in a thunderstorm atmosphere. The Tien-Shan high-altitude cosmic ray station is a unique site for investigations effects of cosmic rays and thunderstorm discharge. "Thunderstorm" detector complex is designed especially for a systematical study of atmospheric discharges by the means of simultaneous recording of the different kinds of radiation. The presence of a widespread extensive air shower trigger set-up at the Tien-Shan station permits to study the role of energetic cosmic ray particles in lightning development. Overview of main results, obtain during last several years at the Tien-Shan are presented. A phenomenological description and theoretical vision of the cosmic rays role in atmosphere processes during thunderstorm are discussed.