ИСТИНА

The soft gamma radiation that appears in the atmosphere as part of the secondary cosmic rays has so far been very poorly studied. In the Polar Geophysical Institute, a gamma-ray detector was created and observations began in 2010 at cosmic ray stations in Apatity and Barentsburg (Spitsbergen archipelago). The presence of a long series of observations at these two cosmic ray stations, as well as the appearance of observational data in other climatic zones (Tiksi, Yakutsk, Mondy (Western Sayany), Rostov-on-Don), together with a new method of comparing data from different stations, allow to make several important conclusions. The measurements are performed by the same type detectors based on the NaI(Tl) crystal, calibrated on the known lines. Detectors are protected by a lead shield from radiation coming from the ground and surrounding objects. In addition to the phenomenon observed at all stations, such as the increase in gamma radiation with atmospheric precipitation (sometimes amplitude of increase reaches 60%), there are regular variations in the gamma background. This is the daily and annual variation of gamma radiation. The characteristics of both variations differ from those observed in other cosmic-ray detectors (a neutron monitor and a muon detector). The annual variation depends directly on the thickness of the permanent snow cover. The decrease of the gamma-ray flux begins with the appearance of a stable snow cover and the flux reaches a minimum during the maximum thickness of the snow cover. After the melting of snow the radiation flux is quickly restored to its previous level. Seasonal changes in atmospheric temperature do not have a noticeable effect on the annual variation. This conclusion follows from the fact that in Rostov-on-Don, where there is no stable snow cover, there is no annual variation, although seasonal temperature changes are significant. On days with good weather, a clear daily variation is also observed. However, the position of the maximum and minimum of the variation diverges with similar values on neutron monitors.