Spectrum and mass composition of cosmic rays in the energy range 10¹⁵–10¹⁸ eV derived from the Yakutsk array data

Yu. G. Shafer Institute of Cosmophysical Research and Aeronomy, 31 Lenin Ave., 677980 Yakutsk, Russia

^a e-mail: s.p.knurenko@ikfia.ysn.ru
^b e-mail: tema@ikfia.ysn.ru

Abstract

A spectrum of cosmic rays within energy range 10¹⁵ − 3 × 10¹⁷ eV was derived from the data of the small Cherenkov setup, which is a part of the Yakutsk complex EAS array. In this, work a new series of observation is covered. These observations lasted from 2000 till 2010 and resulted in increased number of registered events within interval 10¹⁶–10¹⁸ eV, which in turn made it possible to reproduce cosmic ray spectrum in this energy domain with better precision. A sign of a thin structure is observed in the shape of the spectrum. It could be related to the escape of heavy nuclei from our Galaxy. Cosmic ray mass composition was obtained for the energy region 10¹⁶–10¹⁸ eV. A joint analysis of spectrum and mass composition of cosmic rays was performed. Obtained results are considered in the context of theoretical computations that were performed with the use of hypothesis of galactic and meta-galactic origin of cosmic rays.