PECULIARITIES OF HARD COSMIC RADIATION VARIATIONS NEAR THE GROUND SURFACE IN ACCORDANCE WITH GEOMAGNETIC ACTIVITY CHANGES

The mechanism of primary cosmic particle transformation into secondary radiation near the ground surface is analysed. It is known that the main part of secondary cosmic radiation consists of muons. They are formed after nuclear reactions between primary protons and the nuclei of atmospheric gases. Maximum muon concentrations are formed at an altitude of 15 km from the ground surface. Because of a short existence time of muons (2 μs), the amount of these particles near the ground surface depends on variations in the altitude of the above‐mentioned atmospheric layer. Therefore, an unstable flux of muons is registered near the ground surface. Their variations are connected with the Sun's radiation instability, geomagnetic field variations, meteorological process changes, etc. Measurements of the hard cosmic radiation component only near the ground surface are carried out. To this purpose protection of the detector of gamma‐spectrometer was improved. Small gaps between lead plates were made to abolish the shower phenomenon caused by cosmic radiation and the effect of weak‐energy particles and as a result to improve the measurement accuracy. It is defined that lead protection of the thickness of 9 cm of the detector fully absorbs muons with 1,6 MeV energy. It is registered that the gamma‐quanta of 1,6 MeV energy of radionuclide 232Th lose 70 % of the initial energy only in the same lead protection. In 2001–2002 a study was made of the course of the hard cosmic ray flux (HCRF) near the ground surface in four energy intervals: 1 ‐ 0,3–1,2 MeV, 2 ‐ 1,2–1,6 MeV, 3 ‐ 1,6—4 MeV, 4–4 MeV and more. Various course of the HCRF in the mentioned intervals is obtained.