ИСТИНА

The signals from particles of extensive air showers in the energy region of 10^17-10^20 eV in both the surface and underground scintillations detectors of the Yakutsk array are calculated using CORSIKA 6.99 code and GEANT4 software packages within the framework of QGSJET II, EPOS 1.99 and GHEISHA 2002 hadron interaction models and compared with experimental data. Suggestions to adjust the models of hadron interactions with the help of data on the vertical muon energy spectrum and on the calorimeitric estimates of energy of the primary particles have been proposed. The simple method to estimate the vertical muon energy spectrum has been suggested. Simulations showed a deficit of muons in case of the QGSJET II model and a profound enhancement of muons in case of the EPOS 1.99 model. It is shown that a transition from a heavy primary composition to the proton primaries at energies (1-2.6)*10^18 eV might be observed.