Large-scale distribution of cosmic rays in right ascension as observed by the Yakutsk array at energies above $10^{18}$ eV

TL;DR

This study analyzes cosmic ray arrival directions above 10^18 eV using Yakutsk array data from 1974 to 2008, revealing anisotropy and potential sources within specific right ascension ranges.

Contribution

It provides the first harmonic analysis of cosmic ray anisotropy over a large energy range using long-term Yakutsk data, identifying possible source regions.

Findings

Significant contraction of RA distribution width at energies 10^19 to 1.78×10^19 eV.

Detection of anisotropy suggesting potential cosmic ray sources within RA 15° to 45°.

First harmonic phase and amplitude estimations across energy intervals.

Abstract

We present the results of searches for anisotropy in the right ascension ($RA$) distribution of arrival directions of cosmic rays (CRs) detected with the Yakutsk array during the 1974--2008 observational period in the energy range above $10^{18}$ eV. Two methods of analysis are applied to two sub-samples of the data. Particularly, estimations of the first and second harmonic amplitudes are given, as well as the first harmonic phase in adjacent energy intervals. Analysis of variance demonstrates a significant contraction of the minimal width of the $RA$ distribution in the energy bin $(10^{19},1.78\times10^{19})$ eV with respect to the isotropic distribution, which may be attributed to a possible source of CRs within the interval $RA\in(15^0,45^0)$.