Neutron bursts associated with thunderstorms

The basis of our analysis is the observation of the simultaneous enhancements of the gamma ray and neutron fluxes detected in 2009-2010 during thunderstorm ground enhancements at the mountain altitude of 3200 m. We investigate the correlated time series of the gamma rays and neutrons measured by the surface particle detectors of Aragats Space Environmental Center. The photonuclear reactions of the gamma rays born in the runaway breakdown (RB, now referred to as relativistic runaway electron avalanche, RREA) process with air were considered as the main process responsible for the copious neutron production. We consider also the mesoatom nuclei decay as a possible source of the additional neutrons registered by the neutron monitor due to enhanced population of the negative muons accelerated in the thunderclouds.