An analysis of the arrival directions of the highest energy cosmic rays

Abstract

The arrival directions of cosmic rays with energies of at least 1019 eV, recorded at four different latitudes on the Earth's surface, were analysed. A variety of procedures were used to ascertain whether the data available are consistent with the hypothesis that cosmic rays arrive equally from all directions. Because of difficulties in using the full information of arrival directions on the celestial sphere resulting from instrumental uncertainties, a series of circular analyses in right ascension were made. The techniques not only included harmonic analysis but also other statistical methods. The results of the analyses indicate that the data are consistent with the hypothesis that the cosmic rays arrive uniformly from all directions. However, the data suggest that there may be a tendency for the highest energy cosmic rays to arrive more frequently from the direction of the centre of the local supercluster. More data are need to verify or reject this hypothesis. Suggestions for further methods of analysis are given.