Observing the second knee in the PCR spectrum in the region of 1017 eV using the method of local muon density spectra

Abstract

The results from measuring EAS local muon density spectra at ultrahigh energies of primary particles are reported. These spectra are recorded by two instruments at the NEVOD experimental complex (MEPhI, Moscow). Muon bundles in inclined EAS at zenith angles exceeding 55° are registered by the DECOR coordinate detector. Mostly near-vertical muon bundles are registered at the bottom plane of scintillation counters in the calibration telescope system positioned underwater at a depth of approximately 9 m. The results from fitting the local muon density spectra measured by both instruments at primary particle energies below and above 10¹⁷ eV confirm the presence of the second knee (an increase in the slope) in the energy spectrum of cosmic rays in this region.