Variations of gamma-ray during thunderstorm by observations in Yakutsk

Abstract

The paper presents the results of a study of the increase in the gamma background in the surface layer of the atmosphere during near thunderstorms in Yakutsk (based on the Cosmic Ray Spectrograph of the IKFIA SB RAS). To register the gamma background, scintillation detectors based on NaI (Tl) crystals with a size of 63mm x 63mm are used. The range of measured energies is 20-1900 keV. The detectors are closed from the sides and bottom with lead (5 cm) and placed in thermoboxes with a glass window. The detector is located on the roof of the Cosmic Ray Spectrograph building in Yakutsk. Also, synchronous registration of the atmospheric electric field strength was carried out using an atmosphere electric field – mill sensor (with measurement range +/- 50 kV / m).The data of continuous recording of an analog signal from a detector during the nearest thunderstorms of 2018 were considered. The analog signal from the gamma detector was fed to the first channel of the E20-10 ADC (L-Card) and recorded continuously on the computer hard disk for one hour (during a thunderstorm) in series of 10 minutes. A signal from an active broadband dipole P-10 antenna (0.9 kHz - 900 MHz bandwidth) was fed to the second channel and was also recorded in one file together with the signal from the gamma detector. Synchronous recording of signals from the gamma detector and from the antenna allows accurate timing of gamma photons to electromagnetic signals from nearby lightning. In the studied thunderstorms, based on the results of the analysis of the data obtained, statistically significant variations in the count rate and shapes of the spectrum of gamma – ray at the moment of lightning discharges were found.