Cosmic ray anisotropy

The distribution of doublets at E>1019 3 eV (Fig.3c) is more isotropic. It is possible that at these energies the formation of doublets starts at the expense of superheavy nuclei fragmentation. To appreciate the origin of doublets we considered the distribution of showers parallel with the distribution of doublets (Fig3b) in the same energy interval. In the distribution of showers the some maxima are observed at b <3° (exceese of the number of showers relative to expected is 2.7g=(29-17.5)/, at 21°>b>15° etc. However, the maximum in the distribution of doublets is seen at b <3° only. This means that the maximum number of doublets appears where there is the exceed particle flux. Other maxima in the particle distribution are most likely formed by accident and therefore maxima from these directions in the distribution of doublets do not observed. So, the arrival directions of doublets (clusters) can be an indicator of cosmic rays anisotropy. It is important in the case when the cosmic ray anisotropy cannot be detected because of the small statistic. 

Key words cosmic rays of ultrahigh energy, extensive air showers, anisotropy, clusters,... 

There is no significant anisotropy of cosmic rays at any energy, not even at the highest energies, beyond the GZK cutoff. Only at those highest energies is there a persistent hint that events at quite different energies occasionally cluster into pairs and triplets in the sky in the arrival direction, and this is hard to understand in almost any model. 

Obviously, if we could understand the sky distribution of events at these extreme energies, then the option of using pulsars would become very attractive. For particles with a single charge as protons, the anisotropies in arrival directions would be severe, but for iron nuclei this constraint would be much alleviated. Therefore, the option of considering pulsars entails an interpretation as iron particles, inconsistent at the transition from galactic to extragalactic cosmic rays at about 3 EeV, but conceivable at a possible transition from one source population to another at the expected GZK cutoff. 

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