Nonstationary phenomena in cosmic rays with <Emphasis Type="Italic">E</Emphasis><Subscript>0</Subscript> ≤ 10<Superscript>18</Superscript> eV according to the data of the Yakutsk EAS array

The energy spectrum of cosmic rays and the fraction of muons with the threshold 1.0secθ GeV in the total number of charged particles in extensive air showers with energy E ₀ ≥ 10¹⁷ eV according to Yakutsk array data collected during 35 years of its continuous operation in 1978–2012 have been analyzed. It has been shown that these characteristics are noticeably different in different time periods. Before 1996, the integral intensity of the spectrum at E ₀ = 10¹⁷ eV varied near one stable position and then began to increase. It increased by (45 ± 5)% in seven years and, then, began to decrease. This phenomenon was accompanied a similar change in the fraction of muons and was caused by a significant increase in the average weight of the chemical composition of cosmic rays after 1996 as compared to preceding years.     

Portion of muons with a threshold energy above 1 GeV in extensive air showers with ultra-high energies,according to the Yakutsk EAS array data

Characteristics of the muon component in extensive air showers and the fluctuations of muons are considered. In this work, we compare experimental data with computations performed for various models of the hadron interactions of protons and iron nuclei. The aim of this analysis is to obtain information on the mass composition of cosmic rays in an ultra-high energy region.     

On the composition of cosmic rays with E 0 ≥ 1017 eV according to the Yakutsk EAS array data

The energy spectrum and anisotropy of primary cosmic rays, as well as the lateral distribution functions of electrons and muons in extensive air showers (EASs) with E ₀ ≥ 10¹⁷ eV, are presented according to the Yakutsk EAS array data. It has been shown that the spectrum and lateral distribution functions in some energy ranges have different shapes for the particles that arrive from the disc of the Supergalaxy (Local Supercluster of galaxies) and from the other part of the celestial sphere. This is interpreted as the manifestation of the interaction of extragalactic primary cosmic rays with the gas of the Supergalaxy that possibly leads to the production of new ultra-high-energy particles.     

Muon content of ultrahigh-energy air showers: Yakutsk data versus simulations

A sample of 33 extensive air showers (EASs) with estimated primary energies above 2 × 10¹⁹ eV and high-quality muon data recorded by the Yakutsk EAS array is analyzed. The observed muon density is compared event-by-event to that expected from CORSIKA simulations for primary protons and iron using SIBYLL and EPOS hadronic interaction models. The study suggests the presence of two distinct hadronic components, “light” and “heavy.” Simulations with EPOS are in good agreement with the expected composition in which the light component corresponds to protons and the heavy component to iron-like nuclei. With SIBYLL, simulated muon densities for iron primaries are a factor of ∼ 1.5 less than those observed for the heavy component for the same electromagnetic signal. Assuming a two-component proton-iron composition and the EPOS model, the fraction of protons with energies E > 10¹⁹ eV is 0.52_−0.20^+0.19 at the 95% C.L. The text was submitted by the authors in English.     

Electrons and muons in extensive air showers of energies E 0≥3×1017 eV: Yakutsk array data and QGSJET model

The results obtained from an analysis of the 1974–1998 Yakutsk array data on muons with threshold energy E _μ ≈ 1.0 × secθ GeV and on all charged particles (electrons and muons) in extensive air showers (EAS) are reported and compared with the results of calculations based on the model of quark-gluon strings with jets. For energies of E ₀≤3×10¹⁸ eV and zenith angles of θ≤45°, the results of the model calculations are consistent with the measured properties of the showers, while, for higher energy EASs, there are considerable discrepancies, which are probably due to the change in the development of the shower cascade in the region E ₀≥3×10¹⁸ eV.     

Energy Spectrum of Ultrahigh-Energy Cosmic Rays according to Data from Ground-Based Scintillation Detectors of the Yakutsk EAS Array

Results obtained from an analysis of the energy spectrum of cosmic rays with energies in the region of E₀ ≥ 10¹⁷ eV over the period of continuous observations from 1974 to 2017 are presented. A refined expression for estimating the primary-particle energy is used for individual events. This expression is derived from calculations aimed at determining the responses of the ground-based and underground scintillation detectors of the Yakutsk array for studying extensive air showers (EAS) and performed within theQGSJET-01-d, QGSJET-II-04, SIBYLL-2.1, and EPOS-LHCmodels by employing the CORSIKA code package. The new estimate of E₀ is substantially lower than its counterpart used earlier.     

Correlations between the arrival directions of ultrahigh energy cosmic rays and the large-scale structure of the universe

We present the results of analyzing the arrival directions of cosmic rays with energies E ₀≥ 4×10¹⁷ eV and zenith angles θ≤45° detected at the Yakutsk setup during 1974–2000. It is shown that increased particle fluxes exceeding the anticipated random distribution levels by 4–5)σ arrive from the galactic plane at E ₀≈(2–4)×10¹⁸ eV and from the supergalactic plane at E ₀≥8×10¹⁸ eV.     

Yakutsk EAS array data on the variations in intensities of the highest energy cosmic rays

The results of analysis of arrival frequency of cosmic rays with energies E ₀≥4×10¹⁷ eV are presented based on the data collected on the Yakutsk array during its 24 years of continuous operation (1977–2000). It is shown that the intensity of cosmic rays is variable. At E ₀≤(3?5)×10¹⁸ eV, the (2–3)-month data show many deviations by (3–4)σ from the mean level. At E ₀≥10¹⁹ eV, the intensities steadily decrease, on the average, by 1.5 times during the time period considered.     

Complexation of pyrene and anthracene with human blood plasma

We have studied the interaction between polycyclic aromatic hydrocarbons (pyrene and anthracene) with human serum albumin (HSA) and human blood plasma. We have shown that the increase in the fluorescence intensity and the decrease in the polarity index of pyrene on going from an aqueous solution to a pH 7.4 buffer solution of HSA suggests that polycyclic aromatic hydrocarbons are localized in the hydrophobic microphase of the proteins. The increase in the fluorescence intensity for anthracene and pyrene, and also the decrease in the polarity index of pyrene on going from HSA to blood plasma is connected with the fact that polycyclic aromatic hydrocarbons can bind both to plasma proteins and to plasma lipids. When sodium dodecyl sulfate (SDS) is added to the blood plasma in a concentration greater than the critical micelle concentration, we observe an increase in the fluorescence intensity and the polarity index of pyrene. We hypothesize that this is connected with localization of pyrene near the interface between the hydrophobic and hydrophilic phases of the protein-SDS system. We have established that SDS leads to a change in the structure of blood plasma proteins and promotes escape of polycyclic aromatic hydrocarbons from the protein globules. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 3, pp. 379–382, May–June, 2008.