Second Knee on the Spectrum of Cosmic Ray at Energies ∼1017 eV by Long-Term Observations of Small Cherenkov EAS Array

Abstract

The paper presents the cosmic ray spectrum by the Small Cherenkov Yakutsk array data for 20 years of continuous observation. It has been shown by measurements that in the cosmic ray spectrum there is a break in the slope at energy ∼10¹⁷ eV. The reliability is based on the spectra of other compact array experiments and simulations to check for systematic uncertainties, which could affect the shape of the spectrum. In addition there is a change in mass composition of cosmic rays obtained from longitudinal development of air showers with energy 10¹⁶–10¹⁸ eV.