ИСТИНА

At the polar stations Apatity and Barentsburg continuous monitoring of the background gamma radiation (20-800 keV) coming from the atmosphere is carried out since 2010. The database also contains data from a number of mid-latitude stations in recent years. All measurements were made by detectors of the same type made in Polar Geophysical Institute. At all stations, during the entire period of observations, we observe a phenomenon which was not noted by other authors: an increase in the gamma radiation background during precipitation. Our additional experiments showed that these increases are not associated either with radionuclides in precipitation or with an increase of radon concentration in the ground layer of air. The increases are observed only in the electromagnetic component, which is produced in the atmosphere by cosmic rays. The amplitude of increases reaches 100% of the level of clear weather the day before, although a typical increase is 30-50%. The duration of such increase corresponds to the duration of precipitation and varies from 2-3 hours to a day or more. The complex processing of these data showed that the characteristics of events (such as amplitude, duration, rise and fall rates, total energy) at all station depend on seasons. At the same time, the characteristics turned out to be little dependent on the location of the station (polar or mid-latitude). It indicates that the increase in the gamma background during precipitation is due to a unified mechanism that changes the conditions for the interaction of cosmic rays with the atmosphere. A hypothesis is proposed to explain this phenomenon.