Neutron Bursts during CloudtoGround Discharges of Lightning

The relationship between neutron bursts and atmo� spheric electric and geomagnetic fields during thun� derstorms in Yakutsk in 2009–2012 was studied exper� imentally using the precise data obtained by the cos� mic ray spectrograph at 61°59.362′ N, 129°41.874′ E (altitude above sea level, 94 m). The spectrograph con� sists of a 24�NM�64 neutron monitor and four muon telescopes at the 0, 7, 20, and 40 m water equivalent levels that are capable of measuring particle intensity from 5 directions (vertical, and 30 and 60 s from the north and the south). The neutron monitor is based on SNM�15 gas discharge counters; the muon telescopes, on SGM�14 counters. Its electrostatic fluxmeter (range, +/–50 kV m –1 with an error of 1 V m –1 ) was calibrated in an artificial electric field. A second fluxmeter is positioned 4 km away from the monitor, on the roof of the Institute building. The fluxmeter records lightning discharges with a resolution of 1 s in a radius of 10–15 km. The 0.5 second data of an FEG� type ferromagnetic magnetometer (manufactured by Danish Meteorological Institute) with a dynamic measurement range of ± 3200 nT and an error of 0.1 nT were also used. The magnetometer positioned