Observation of cosmic-ray anisotropy in the decade below 1 PeV with a pentagon array

Abstract

The study of the anisotropy of the arrival directions is an essential tool to investigate the origin and propagation of cosmic rays primaries. A pentagon array has been designed to collect data around the knee region of cosmic ray spectrum. The experimental results of this array obtained from October 2016 to October 2017. During this period, more than $5.3\ifmmode\times\else\texttimes\fi{}{10}^{5}$ extensive air shower events at energies in the decade below 1 PeV has been accumulated by this array at Sharif University of Technology in Tehran ($35\ifmmode^\circ\else\textdegree\fi{}4{3}^{\ensuremath{'}}\mathrm{N}$, $51\ifmmode^\circ\else\textdegree\fi{}2{0}^{\ensuremath{'}}\mathrm{E}$, 1200m $\mathrm{a}.\mathrm{s}.\mathrm{l}=890\text{ }\text{ }\mathrm{g}\text{ }{\mathrm{cm}}^{\ensuremath{-}2}$). In analyzing the data set, we have used appropriate techniques of analysis and considered environmental effects. We report the analysis of the sidereal anisotropy of Galactic cosmic rays (GCRs). In this analysis, in addition to the Compton- Getting effect due to the motion of the earth in the Galaxy, an anisotropy has been observed which is due to a unidirectional anisotropy of cosmic ray flow along the Galactic arms.