Vol 81, No 4 (2017)

A brief survey of the data on the isotopic composition of superheavy nuclei in galactic cosmic rays is presented. The scientific goals of the planned experiment are outlined, and the design of the NUCLEON-2 scientific equipment is given.

The TUS telescope, part of the scientific equipment on board the Lomonosov satellite, is the world’s first orbital detector of ultra-high energy cosmic rays. Preliminary results from analyzing unexpected powerful signals that have been detected from the first days of the telescope’s operation are presented. These signals appear simultaneously in time intervals of around 1 μs in groups of adjacent pixels of the photodetector and form linear track-like sequences. The results from computer simulations using the GEANT4 software and the observed strong latitudinal dependence of the distribution of the events favor the hypothesis that the observed signals result from protons with energies of several hundred MeV to several GeV passing through the photodetector of the TUS telescope.

Based on experimental data obtained by the GAMMA array for the knee energy region, an anomaly is found in the mass composition of primary cosmic rays arriving from the region of the Vela cluster. An original difference method is used that offers high sensitivity, protection against accidental experimental errors, and the ability to separate anomalies associated with the laboratory coordinate system from those in celestial coordinates. Allowing for the multiple scattering of charged particles in the galactic magnetic fields allows parts of the sky not directly visible from the array to be studied.

The duration of gamma ray bursts (GRBs) is usually characterized by time interval t₉₀, in which the total number of registered counts grows from 5 to 95%. Classes of short and long GRBs were first detected in analyzing the BATSE experiment data from the Compton Gamma Ray Observatory (CGRO); burst duration separation point was found to be t_90lim ~2 s. A group of bursts of intermediate duration was first detected in analyzing the data of the same experiment in 1999 in the interval of ~1 to ~40 s with an average event duration of 〈t₉₀〉 ~ 3.5 s. The results from analyzing the catalog of gamma-ray burst data selected while ground processing BATSE data (i.e., the catalog of nontriggered events) showed that the intensity of intermediate bursts is lower than that of short and long bursts. Preliminary results from investigating the GBM catalog (onboard the Fermi Space Observatory) and the BAT catalog (onboard the Swift satellite) confirm the detection of events with similar properties.

A combined approach to distinguishing extensive atmospheric showers (EASes) from gamma rays, based on analyzing Imaging Atmospheric Cherenkov Telescope (IACT) images and shower parameters reconstructed using data from a nonimaging (timing) array, is investigated. The study is conducted with simulated data on the registration of Cherenkov radiation from an EAS. The optimum set of combined parameters, the efficiency of the multivariate approach, and the dependence of the background suppression factor on energy and distance are determined. The findings are compared to those from the operation of an isolated IACT. It is shown that in the >50 TeV range of energies, the background can be suppressed by a factor of 100 even at distances of up to 450 m from an IACT telescope.

Particle acceleration by shock waves in old supernova remnants is studied. The radiative loss of gas behind the front of a shock wave, the streaming instability of magnetohydrodynamic waves, and the damping of waves on neutral atoms are considered. The calculated spectra of electromagnetic emissions are compared to observations of supernova remnant IC 443.

The propagation of ultrahigh-energy nuclei in an expanding Universe filled with background electromagnetic radiation is considered. A numerical method for solving the inverse problem for the equation of cosmic-ray transport is developed that allows the spectrum of sources to be determined from the cosmic-ray spectrum observed near the Earth. The spectra of injected protons and nuclei in extragalactic sources are found by assuming that they are functions of the magnetic rigidity of particles. The data from observations obtained in the Auger experiment are used.

An estimate of the influence the finiteness of particle velocity has on the results of a fractional differential (anomalous) model of cosmic ray propagation in the Galaxy with Lévy flights developed by the authors is considered. The results from Monte Carlo simulations of particle diffusion in random walk models with finite and infinite velocities are presented. It is shown that considering particle velocity finiteness has almost no effect on the cosmic ray energy spectrum obtained for E > 1 GeV in the anomalous diffusion model with Lévy flights for nearby young sources.

A simple “knee-like” approximation of the Lateral Distribution Function (LDF) of Cherenkov light emitted by EAS (extensive air showers) in the atmosphere is proposed for solving various tasks of data analysis in HiSCORE and other wide angle ground-based experiments designed to detect gamma rays and cosmic rays with the energy above tens of TeV. Simulation-based parametric analysis of individual LDF curves revealed that on the radial distance 20−500 m the 5-parameter “knee-like” approximation fits individual LDFs as well as a mean LDF with a very good accuracy. In this paper we demonstrate the efficiency and flexibility of the “knee-like” LDF approximation for various primary particles and shower parameters and the advantages of its application to suppressing proton background and selecting primary gamma rays.

The design for the TAIGA-HiSCORE array, a part of the TAIGA Gamma Ray Observatory, is considered. The observatory is being constructed in the Tunka Valley, 50 km from Lake Baikal. Preliminary results obtained using the first 28 optical stations of the array are presented.

The Tunka-Grande scintillation array is described. The first results from its operation are presented. The prospects for studying primary cosmic rays in the energy range of 10¹⁶ to 10¹⁸ eV during simultaneous registration of the Cherenkov and charged particle components along with radio emissions from extensive air showers are discussed.

The procedure for and results from a search for showers generated by such neutral particles as high energy gamma rays and astroneutrinos are presented. A comprehensive analysis of data on electrons, muons, and EAS Cherenkov light, and their response time in scintillation and Cherenkov detectors, is performed.

A coordinate tracking unit based on drift chambers (CTUDC) for registering single muons and muon bundles at large zenith angles is created at the MEPhI. The unit consists of multi-wire drift chambers (DCs) with large drift gaps. These DCs were used earlier for the neutrino channel on the U-70 accelerator. The CTUDC consists of two coordinate planes with 8 drift chambers in each, assembled on the opposite sides of the NEVOD Cherenkov water detector (CWD). The effective area of the unit is 29.6 m². The CWD trigger system and DECOR coordinate-tracking detector provide timestamps for the drift chambers. The first results from the registration of single muons and muon bundles by the unit in combination with other detectors of the NEVOD experimental complex are presented.

The NEVOD-EAS array is now being installed at MEPhI to determine the sizes, directions of arrival, and positions of the axes of extensive air showers (EAS), different components of which are recorded by the detectors of the NEVOD experimental complex. The central part of the NEVOD-EAS array, which contains four clusters of scintillation detector stations designed to record a shower’s electron–photon component, was created and put into operation in 2015. A description of the shower array measuring system and the results from reconstructing extensive air showers recorded in the first 49-day series of experiments are presented.

The results from investigating the near-horizontal flux of cosmic ray muons are presented. In this range, so-called albedo muons (atmospheric muons that have penetrated into the ground and scattered into the upper hemisphere) are detected. Albedo muons are one of the main sources of the background in neutrino experiments. Data from a series of measurements performed at the NEVOD experimental complex over 30000 hours of operation are analyzed. The expected muon flux is simulated using the Monte Carlo method, based on two models of multiple Coulomb scattering of muons in the ground: one with point-like nuclei and one with nuclei of finite size. The results from measuring muon intensity in the 85°–95° range of zenith angles are compared to those from simulations.

The Lebedev Physical Institute of the Russian Academy of Sciences and the Skobeltsyn Institute of Nuclear Physics of Moscow State University conduct experiments using nuclear photoemulsion to study the internal structure of large objects via muon radiography. Analysis of an experiment in a mine in Obninsk belonging to the Geophysical Service of the Russian Academy of Sciences is of particular interest. Calculated and experimental data are presented.

The URAN array is designed to study primary cosmic rays in the region of the knee by detecting neutrons produced as a result of interaction between EAS particles and nuclei in the atmosphere or matter near the installation. It consists of 72 detectors mounted on the roofs of experimental buildings and combined into cluster structures of 12 detectors. The registering element is scintillator based on natural boron. The area of each detector is 0.36 m².

Cosmic ray muons at average energies of 280 GeV and muon-induced neutrons are detected by the LVD (Large Volume Detector). An analysis of seasonal variations in the neutron flux, based on data collected over 15 years, is presented. Measuring of the seasonal variations in the specific number of neutrons generated by muons allows us to determine the magnitude of variations in the average energy of the muon flux at the depth of the LVD’s location. The source of the seasonal variations in the total neutron flux is a change in the intensity and average energy of the muon flux. An analysis of the long-term monitoring of the LVD’s low-energy background is also presented.

Results obtained from the measuring the radio emissions from extensive air shower particles with energies higher than 5 × 10¹⁸ eV at a frequency of 32 MHz are presented. A generalized formula is derived to describe the spatial distribution of radio emissions using the main EAS characteristics: energy Е₀ and depth of maximum development of shower Х_max. The approximating function describes the data at average and large distances from a shower axis. The ratio of signal amplitudes at distances of 175 m and 725 m is used to determine Х_max for an average shower with an energy of 1.54 × 10¹⁹ eV, which in our case is equal to Х_max = 769 ± 34 g cm⁻². Within the experimental error, the result for Х_max is consistent with data obtained using EAS Cherenkov light.

Neutron monitors at the Baksan, Moscow, Apatity, and Barentsburg stations are equipped with a unique high-speed registration system that registers the arrival of a pulse with an error of about 1 μs. Analysis of data obtained using the neutron monitors reveals the presence of isolated particle clusters in the flux of high-energy (above tens of GeV) cosmic ray particles. The clusters are known as transients. The neutron monitors detect brief surges of density in the high-energy particle flux. Each surge lasts 20–40 s. The flux density inside the transients is about twice the average level. The transients are isolated by dips that are brief 200–300% drops in the particle flux density, observed in front of and behind each one. It is assumed that a transient is a brief local surge in particle flux density during cosmic ray diffusion and scattering in the interplanetary magnetic field.

The intensity of cosmic rays in a magnetic cloud is calculated. It is found that the duration of the Forbush decrease recovery is determined by the magnetic cloud orientation and the reduction in the magnetic field inside the magnetic cloud as it expands. The formation of the Forbush decrease is described in terms of the contributions from different sources of particles.

The state-of-the-art Yakutsk cosmic ray spectrograph consists of the 24-NM-64 neutron monitor, four muon telescopes of the same type, and SGM-14 gas-discharge counters that detect particles coming from five directions and are installed at levels of 0, 7, 20, and 40 meters of water equivalent. A new complex of four muon telescopes of the same type based on SC-301 scintillation counters that record particles from 13 destinations has now been added to the spectrograph. Acceptance vectors that consider the geometry, geographical position, and energy spectra of the observed cosmic ray variations have been developed for these instruments. Analysis of the data from the new scintillation detectors shows that the count rate is as expected in all directions. The parameters of the acceptance characteristics of the new scintillation telescopes and current detection data are available on the Institute’s website at http://www.ysn.ru/smt.