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

S.P Knurenko,A Sabourov,K.-H Kampert,R Engel,B Pattison,M Fukushima

doi:10.1051/epjconf/20135304004

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.

Highlights

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 extensive air showers (EAS) array
Energy spectrum of cosmic rays (CR) in energy range 3 × (1015–1018) eV could not be studied in detail with compact arrays due to their small acceptance at energy above 1017 eV
In the region (∼3 × 1017–318) eV, the spectrum is shaped by unknown component; here, one may speculate of CR particles interaction with galactic wind and shock acceleration

Summary

INTRODUCTION

Energy spectrum of cosmic rays (CR) in energy range 3 × (1015–1018) eV could not be studied in detail with compact arrays due to their small acceptance at energy above 1017 eV. This effect is smoothed by addition of a new component (of metagalactic or other origin) to the cosmic ray flux near Earth. Presence/absence of significant irregularities in spectra measured by various compact arrays allows one to speculate on the CR origin and propagation in our Galaxy [1, 2]. It is related to medium-sized arrays, capable of effective measuring of cosmic rays flux in a wide energy range (1015–1019 eV). Factors mentioned above enable adopting the unique method, combining the studies of CR spectrum and mass composition aimed at exploration of astrophysical aspect of cosmic rays [3, 4]

METHODICAL ISSUES

Monitoring of the atmosphere

Estimation of primary energy

Energy spectrum of cosmic rays within energy interval 1015–1018 eV

Mass composition