Cosmic rays of extremely high energies and pulsars

Extensive air showers with energy above 4×10¹⁹ eV that were detected at the Yakutsk array from 1974 to 2001 are analyzed. The directions of their arrival are found to correlate with pulsars located in the direction of the Orion Arm of the Galaxy. The origin of cosmic rays is discussed.     

Radio signals from extensive air showers with the energies <Emphasis Type="Italic">E</Emphasis> <Subscript>0</Subscript> ≥ 10<Superscript>19</Superscript> eV according to data from the Yakutsk extensive air shower array

A radio instrument and results obtained from the measurements of the 32-MHz radio signal from particles of extensive air showers (EASs) with energies E₀ ≥ 1×10¹⁹ eV are reported in brief. The data were obtained at the Yakutsk EAS array in 1987–1989 (the first series of measurements) and in 2009–2014 (new series of measurements). The radio signal from EASs with energies above 10²⁰eV was detected at the Yakutsk EAS array for the first time, including the shower with the record energy of ~2×10²⁰ eV for the Yakutsk EAS array.     

Extensive ultrahigh energy air showers and pulsars

Directions of the arrival of extensive air showers (EASes) of ultrahigh energy detected on world EAS arrays are considered. It is found that the directions of the arrival of some EASes correlate with the pulsars located along magnetic field lines of the local (Orion) arm of the Galaxy. The problem of cosmic rays origin is discussed.     

New Method for Estimating the Energy of Extensive Air Showers from Signals of Ground-Based Detectors of the Yakutsk Extensive Air Shower Array

A new method has been proposed for estimating the energy of inclined extensive air showers from signals of ground-based scintillation detectors of the Yakutsk extensive air shower array that are located at a distance of 600 m from the shower axis in the plane of the array and from the calculations of these signals within two hadron interaction models. New estimates of the energy have been obtained for 116 showers detected in different years. It has been shown that the energy spectra of particles of primary cosmic radiation measured at the Yakutsk array are in agreement with world data.     

Multipolar anisotropy of <Emphasis Type="Italic">E</Emphasis><Subscript>0</Subscript> ⩾ 10<Superscript>17</Superscript> eV cosmic rays according to data of the Yakutsk array for studying extensive air showers

The results obtained by analyzing arrival directions for primary cosmic particles characterized by energies in the region E ₀ ⩾ 10¹⁷ eV and zenith angles in the range θ ⩽ 60° and detected at the Yakutsk array for studying extensive air showers (EASs) over the period spanning 1974 and 2009 are presented. It is shown that these events exhibit different anisotropies in different energy intervals.     

Spatio-temporal structure of the muon disk at <Emphasis Type="Italic">E</Emphasis><Subscript>0</Subscript> ≥ 5 × 10<Superscript>16</Superscript> eV from Yakutsk EAS array data

We present the results of our study of the temporal structure of the muon disk at the Yakutsk array in extensive air showers with primary energies E₀ ≥ 5 × 10¹⁶ eV at distances of 250–1500 m from the shower axis obtained using a large muon detector with an area of 184 m² and a detection threshold of E_μ ≈ 0.5 sec θ GeV. We have found two components with different muon disk thicknesses that require significant revisions of our view of the development of extensive air showers.     

Quasars as sources of ultrahigh-energy cosmic rays

The results are presented that were obtained by analyzing arrival directions for cosmic rays that the Yakutsk array for studying extensive air showers recorded between 1974 and 2002 in the energy region E₀ ≥ 5 × 10¹⁷ eV for zenith angles in the region θ ≤ 60°. It is shown that quasars for which the red shift lies in the region z ≤ 2.5 can be sources of these cosmic rays. Ordered structures are observed in the disposition of quasars and in the cosmic-ray arrival directions. These structures can be associated in one way or another with the large-scale structure of the Universe.     

Analysis of anisotropy of cosmic rays with the energy of about 1017 eV by Yakutsk EAS array data

A harmonic analysis of the directions of arrival of cosmic-ray particles with an energy of about 10¹⁷ eV in the vicinity of the registration threshold of the Yakutsk extensive air showers (EAS) array is given. A method for determining the contribution of inhomogeneous observation conditions and seasonal variations of the frequency of extensive air showers to the observed anisotropy is suggested. Taking into account these factors results in a considerable decrease of the amplitude characterizing the degree of anisotropy of cosmic-ray primaries. The amplitude of the first harmonic with respect to the right ascension is (0.45 ± 0.55)%, which shows that no probably significant anisotropy of the primary radiation is observed at 10¹⁷ eV.     

Could primary particles of ultrahigh energy be neutral?

Results are presented that were obtained from an analysis of the nuclear-physics and astrophysical features of extensive air showers of energy in the region E ₀≥10¹⁵ eV that were recorded at the Yakutsk array and other arrays over the world. It is shown that, at some values of E ₀, different data sets display local irregularities that are correlated in energy and which are interpreted as a manifestation of neutral particles of an extragalactic origin. The directions of their arrival point to the Supergalaxy plane (Local Supercluster of galaxies).     

A search for extragalactic sources of cosmic rays in the ultra-high energy domain

The arrival directions of ultra-high energy cosmic rays detected with the Yakutsk extensive air shower array are analyzed in comparison with the available data from other giant arrays. A correlation with the coordinates of active galaxy nuclei as hypothesized sources of ultra-high energy cosmic rays is sought for.     

Investigation of the structure of a muon disk for <Emphasis Type="Italic">E</Emphasis><Subscript>0</Subscript> ≥ 5 × 10<Superscript>16</Superscript> eV according to data of the Yakutsk array for studying extensive air showers

The results are presented that were obtained at the Yakutsk array by investigating the time structure of a muon disk in extensive air showers of primary energy in the region E ₀ ≥ 5 × 10¹⁶ eV at distances of 250 to 1500 m from the shower core. The measurements were performed with a large muon detector that has an area of 184 m² and a detection threshold of E _μ≈0.5secθ GeV and which began operating in November 1995. Two components having different muon-disk thicknesses were discovered, and this requires strong modifications in the currently prevalent idea of the development of extensive air showers. The problem of the existence of E ₀ ≥ 10²⁰ eV events is considered. __________ Translated from Yadernaya Fizika, Vol. 68, No. 1, 2005, pp. 74–88. Original Russian Text Copyright ? 2005 by Glushkov, Dedenko, Sleptsov.     

Anomalous extensive air showers of ultrahigh energies and their arrival directions

Extensive air showers (EASs) of energy above 8×10¹⁸ eV observed from 1974 to 1995 on the Yakutsk EAS array are analyzed. Showers without muonic component are found. From the arrival directions of these showers, two clusters were found, one of which coincides, within the error bars, with a pulsar in the Milky Way Galaxy.     

Mass Composition of Cosmic Rays with Energies above 1017 eV According to the Data from the Muon Detectors of the Yakutsk EAS Array

The lateral distribution of muons in extensive air showers with energies above 1017 eV detected by underground scintillation detectors with a threshold of 1.0 GeV at the Yakutsk array in 1986–2016 has been analyzed. The experimental data on the muon flux density at a distance of 300 m from the shower axis have been compared to the calculations within various models of hadron interactions at ultrahigh energies. The experimental data are in the best agreement with the QGSJet01 and QGSJet II-04 models. The mass composition of cosmic rays in the energy range of (1–30) × 10¹⁷ eV changes from middle nuclei to a purely proton composition.

     

New energy estimates of extensive air showers using signals detected at great distances from the shower axis

On the basis of detailed tables of signals from Yakutsk extensive air shower scintillation detectors that were calculated using the GEANT4 package, the numerical evaluation of the energy E _θ of inclined extensive air showers has been obtained using a pilot signal at a distance of 1000 m from the shower axis and the known zenith angle θ using the CORSIKA package. This original estimate was obtained without using the method of cutting the signal spectra according to lines of equal intensity. We also obtained the values of practical units of measure for signals in ground-based and underground detectors.     

Estimation of the PCR mass composition in the energy range 1017–1019 eV on the basis of multicomponent analysis of the characteristics of EASs detected at the Yakutsk array

The characteristics of longitudinal and radial extensive air shower development derived from the results of detection of the charged particle flux and Cherenkov light in extensive air showers at the Yakutsk array. To estimate the primary cosmic ray composition, a combination of the parameters X_max and ρ₆₀₀ and the database simulated using the CORSIKA code (QGSJET model) for showers generated by five types of nuclei (p, He, C, Si, Fe) in the energy range 10¹⁷–10¹⁹ eV were used. Application of the multicomponent method made it possible to divide the showers into three groups (p + He), C, and (Si + Fe) and estimate their percentage. The error in identifying nuclei in the energy range 10¹⁷–10¹⁸ eV does not exceed 30%.     

Spatiotemporal structure of pulses in detectors of Cherenkov light of extensive atmospheric showers

We calculated the pulses of the Cherenkov light of extensive atmospheric showers in Cherenkov radiation detectors at the Yakutsk array in the framework of the QGSJET-II model. It is shown that the calculated width of a pulse of Cherenkov light in a vertical proton-induced shower of energy of 10¹⁸–10²⁰ eV increases from 50 ns at a distance of 200 m from the shower axis to 700 ns at a distance of 1 km.     

Zur longitudinalen Verteilung der Elektronen in großen Luftschauern

The standard deviationσ of the instantaneous distribution of electrons in extensive air showers at sea level has been measured by coincidence of two spark counters, a cloud chamber providing data on arrival directions and particle densities. The values published up to now were in the range 2<σ<8 ns and the standard time deviationσ ₀ due to instrumental fluctuations was about 4 ns. In this experiment with aσ ₀=1,8 ns mean delaysσ have been obtained between 1 and 2 ns, the values decreasing with increasing particle density. This tendency may be due to the fact that the mean separations of the electrons, taken perpendicular to the shower front, are increasing with distance from the shower axis. The fractional contribution of showers within a given range of sizes, the axes of which came down within a given interval of distances from the counters has been calculated. It was concluded that 80% of the showers triggering the two counters were in the range from 10⁵ to 10⁷ particles. By means of these calculations, using the measured values for the mean delaysσ at different particle densities, a simple curve has been constructed which gives the mean separations of electrons vs distance from the shower axis up to 1000 m and is in good agreement with the experimental data ofLinsley andScarsi for great distances from the shower axis.     

Investigation of primary cosmic rays at energies above 10<Superscript>14</Superscript> eV

A search for sources of primary cosmic rays at energies of 10¹⁴–10¹⁵ eV was performed using the special independent KLARA+Khronotron unit at the Tien Shan Mountain Cosmic Ray Station in a joint experiment of the Lebedev Physics Institute (LPI) and the Central Research Institute for Physics (KFKI). A full data bank of standard events, consisting of 30 million extensive air showers (EASes), was analyzed. Analysis results are presented as maps of the directions of EAS arrival in equatorial coordinates in which the standard deviation of the number of events exceeds a certain value. These could be directions from which neutral primary cosmic particles (e.g., gamma ray photons) arrive from sources of primary cosmic rays. A match is found between separate directions with results, obtained on other stations, and the location of pulsars.     

Search for extragalactic sources of ultrahigh-energy cosmic rays

Possible extragalactic sources of cosmic rays with energies above 4 × 10¹⁹ eV detected at the Yakutsk EAS array are sought. The correlation of the shower arrival directions with objects from Véron’s catalog that are located closer than 100 Mpc from the Earth confirms the observations at the Pierre Auger Observatory, as well as the Greisen-Zatsepin-Kuzmin effect on the spectrum of cosmic rays. The detailed analysis of the data reveals the classes of objects belonging to the active galactic nuclei that are the most probable sources of ultrahigh-energy cosmic rays.     

Small-scale anisotropy and composition of <Emphasis Type="Italic">E</Emphasis><Subscript>0</Subscript> ≈ 10<Superscript>17</Superscript> eV cosmic rays according to data from the Yakutsk array for studying extensive air showers

Results are presented that were obtained from an analysis of arrival directions for cosmic rays of energy in the range E ₀ ≈ 10^16.9–17.2 eV that were recorded by the Yakutsk array between 1974 and 2001 at zenith angles of θ ≤ 45°. It is shown that a considerable part of them form clusters that have small-scale cellular structure. In all probability, these showers are generated by neutral particles of an extragalactic origin.