Small-scale anisotropy of cosmic rays with energies above 3×1018 eV based on data from the Yakutsk EAS facility

We analyze the directions of the arrival of cosmic rays with energies E ₀≥3×10¹⁸ eV and zenith angles θ≤45° recorded by the Yakutsk extensive air shower (EAS) facility during 1974–2000. They are shown to have a small-scale structure with scale sizes of 5°–10°. Enhanced particle fluxes compared to the expected levels for random distributions at (4–5)σ are observed from the Galactic and Supergalactic planes.     

Observation of a Beam of Ultrarelativistic Particles and the Cherenkov Resonance

Previously we have reported the detection of a sequence of three particle arrival events at energies above 10¹⁹ eV during one day and from a small sky region by two extensive air shower (EAS) arrays. We have shown that the probability of a chance coincidence of the three events is very low and suggested the arrival of a short-lived particle beam at the Earth. Here we refine the energies of the recorded particles and discuss a possible beam formation mechanism that explains the observational results.

     

Variable anisotropy of cosmic rays with E 0 ⩽ 1018 eV from Yakutsk EAS array data

Results of a harmonic analysis of the arrival directions for primary cosmic-ray particles with energies E ₀ ? 10¹⁷ eV and zenith angles θ ? 45° recorded on the Yakutsk array over 29 years of its continuous operation (1983–2012) are presented. These events are shown to have different global anisotropies in different time intervals: the phase of the first harmonic φ ₁ = 119° ± 18° and its amplitude A ₁ = 0.030 ± 0.014 in the 1983–1994 samples changed into φ ₁ = 284° ± 13° and A ₁ = 0.033 ± 0.010 in 1998–2010. All of this could be caused by a considerably increased flux of heavy nuclei from the exit of the Galaxy’s local arm after 1996.     

Composition of Cosmic Rays with <Emphasis Type="Italic">E</Emphasis><Superscript>0</Superscript> ⩾ 10<Superscript>17</Superscript> eV Based on Data from the Ground Scintillation Detectors of the Yakutsk EAS Array

The lateral distribution of cascade particles in extensive air showers from cosmic rays with energy E⁰ ? 10¹⁷ eV has been studied at the Yakutsk array by the ground scintillation detectors over the period of continuous observations 1977–2017. The experimental data are compared with those computed with various models for the development of extensive air showers from the CORSIKA software package. The best agreement between the theory and experiment is observed for the QGSjet-01-d model. In the energy range (1?20)× 10¹⁷ eV there is a change in the cosmic-raymass composition from 〈lnA〉 ≈ 2.5 to the proton one.     

A beam of particles in ultrahigh-energy cosmic rays?

Three particles with energies of 36, 35, and 58 EeV arrived from one sky region were recorded by two EAS arrays during a day. The events are assumed to have been produced by the beam of particles that resulted from the interaction of cosmic rays with a relativistic shock front.     

Searches for the sources of cosmic rays with energies (1–4)×1017 eV using the Yakutsk EAS array

We analyze the arrival directions of cosmic rays with energies E ₀≈(1–4)×10¹⁷ eV and zenith angles θ≤53≤ detected with the Yakutsk extensive air shower (EAS) array during 1974–2001. We show that ～10% of them form many clusters correlated with the Supergalactic plane. Enhanced particle fluxes arrive from the Supergalactic plane and the regions that are symmetrically adjacent to it at angles ±b _SG ≈ 6°.5. The relatively high concentrations of clusters of galaxies and quasars that bear a relationship to the large-scale structure of the Universe are observed in these regions.