Energy spectrum and mass composition of primary cosmic rays at energies 1015–1018 eV

Data on muon and electron components of extensive air showers (EAS) (obtained with the EAS MSU array) were used to derive the primary cosmic ray (PCR) mass composition. It is shown that for energies beyond the knee at energy 3 × 10 15 eV the abundance of heavy nuclei increases with energy. But at energies above 10 17 eV the abundance of light nuclei starts to grow. The primary cosmic ray spectrum in the range 10 15 –10 18 eV is analyzed. It is shown that at energies above 10 17 eV the additional component appears and it differs from the bulk of Galactic cosmic rays generated by shocks in SN remnants.