Modelling of the electron acceleration and multiplication in the electric fields emerging in terrestrial atmosphere

Thunderstorm ground enhancements, fluxes of electrons, gamma rays, and neutrons originated in the thunderstorm atmospheres are controlled by the strength of the atmospheric electric fields. If the strength is above a threshold value, that is inversely proportional to the air density, a Relativistic Runaway Electron Avalanche (RREA) is unleashed, in which large-scale multiplication of the particles took place. The second process, Modification of the electron energy spectra (MOS) operates on much less scales however is effective for almost all strengths of atmospheric electric fields. In the series of simulations with the CORSIKA code we show that MOS process can be responsible for long lasting TGEs recently discovered on Aragats