Izvestiâ Akademii nauk SSSR. Seriâ fizičeskaâ
ISSN (print): 0367-6765 Founder: Russian Academy of Sciences Editor-in-Chief: Khokhlov D.R., corresponding member RAS, Doctor of Sc., Full Professor Frequency / Assess: 12 issues per year / Subscription Included in: White List (3rd level), Higher Attestation Commission List, RISC,
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Comparative analysis of the technogenic factors affecting the gamma-quanta counting rate in LSD and LVD underground experiments
We presented a comparative analysis of the gamma-quanta counting rate data with energies greater than 0.5 MeV from the underground LSD (operated from 1984 to 1999) and LVD (data collection from 1992 to the present) installations. These detectors are identical in structure and have identical scintillation counter modules with a volume of 1.5 m3. They are ~700 km from each other, in different regions of Italy with different seismic activity, under different mountain ranges, and have different ventilation systems. Data from both detectors for 1997 are presented. The effect of the ventilation system on variations in radon concentration in underground premises is shown.
Copyright (c) 2025 Russian Academy of Sciences
Sources of background events in LVD experiment
We presented the results of modeling background events in the Large Volume Detector – LVD (Gran Sasso Laboratory, Italy) from natural radioactivity of the rock and detector construction materials. Contributions to the overall background of events from various sources are calculated and compared with experimental data.
Diurnal wave of the ground level electric field of fair weather in mountains and its influence on the muon intensity
A diurnal wave of the ground level electric field of a non-standard type is regularly observed at the Carpet air shower array of the BNO INR RAS (43.3° N, 42.7° E), located in a mountain valley at an altitude of 1.7 km above sea level. In the period from July 29 to September 6, 2019, which included two magnetic storms, a change in the sign of the diurnal wave of the muon intensity with an energy of more than 100 MeV recorded by the array was observed. The diurnal behavior of pressure, temperature and ground level electric field did not change. Using the case of diurnal wave inversion, an estimate was made of the contribution of the regularly measured disturbance of the atmospheric electric field to the variations in muon intensity. During the study, previously unnoticed morning-evening variations of terrestrial origin were revealed.
Search for correlations of solar activity with 55Fe, 60Co nucleus decay parameters
Temporal variations of nuclei decay parameters are actively searched now; their detection may be a signal of new physical effects of cosmic origin. Correlations of intensity of 60Co, 54Mn and 55Fe weak decay parameters with solar activity, with solar flares, were observed. In our work, correlations of X-class solar flares with 60Co and 55Fe decay rate variations measured via decay γ-ray detection by semiconductor detectors. For 55Fe decay the significant deviations of decay counting rate from the expected rate observed at the level -0.2% correlated with solar flares. For 60Co decay four similar events were detected with deviations at a level of ~0.4%. All decay rate deviations start from 30 to 155 hours before solar flare moments at confidence level of 90%.
Analysis of geo-efficient coronal mass ejections on May 10–12, 2024, in the flux of solar wind and cosmic rays at ground level
A method for determining a complex operational predictor of space weather disturbance is proposed. The calculations are based on different types of time series: solar activity in the radio and gamma bands, solar wind energy, variations in the flux of cosmic rays according to the data of the world network of neutron monitors and the multidirectional muon hodoscope. The technique has been tested in the analysis of a powerful geomagnetic disturbance (Dst = −412 nT). The sequence of predictors was obtained in "real" time ranging from 2–3 days to several hours.
Analysis of the powerful Forbush decreases of 2024 based on data from unshielded neutron detectors of the experimental complex NEVOD
In the Experimental complex NEVOD (MEPhI, Moscow), the "Neutron" and PRISMA-36 facilities, consisting of unshielded neutron detectors, are being operated. The results of the analysis of two most powerful Forbush decreases detected at these facilities in the first half of 2024 are presented and compared with the Moscow neutron monitor data. The obtained dependence of the disturbance amplitude on the thickness of the substance above the detector is presented.
Cosmic ray variations during extreme geomagnetic disturbances on May 9–15, 2024
We presented the results of the analysis of solar and geomagnetic activity, variations in cosmic ray fluxes in the period May 9–15, 2024. Data from a network of ground-based neutron monitors, data from measurements of cosmic rays by CARPET instruments and neutron detectors located at the Dolgoprudnenskaya Scientific Station of the LP1 RAS, at the Eurasian National University (Astana, Republic of Kazakhstan) and at the astronomical complex KASLEO are used (The Argentine Andes). We studied the characteristics of the Forbush decrease in cosmic ray fluxes on May 10, 2024, and the subsequent increase in cosmic rays on May 11. The results obtained indicate the different nature of these effects.
Energy of the first protons and rate of their acceleration
Theoretical estimates of the acceleration times of solar electrons and protons during the process of “magnetic detonation” — the development of eruptive flares — are made. The relationship between the acceleration rate and the energy of the first protons arriving in the Earth’s orbit is studied using the example of observations of four events in May–June 2024. Eruptive flares (proton and non-proton) can be classified by the electric field strength (by the time of electron acceleration to 100 keV and the moment of arrival of the first protons) and the duration of observation of electron radiation above 100 keV (the time available for proton acceleration >100 MeV).
Some features of the solar proton event of 27.08.2022
The solar proton event of 27.08.2022 was recorded by spacecraft near the Earth, as well as by the Parker Solar Probe spacecraft, located at 0.38 AU from the Sun. During this event, a rare phenomenon was observed, the acceleration of protons to energies of tens of MeV in interplanetary space presumably between the converging shock fronts. An unusual delay in the fluxes of solar protons with energies above 10 MeV was also observed, as measured by satellites in Earth orbit, compared to the proton fluxes measured by spacecraft at the L1 Lagrange point.
Solar cosmic rays and hard X-ray radiation from solar flares in the first half of 2024 according to experiments on the Moscow university satellites of the CubeSat format
We presented the results of observations of electrons of solar cosmic rays and hard X-ray radiation from solar flares in the first half of 2024 in experiments on CubeSat satellites with a low polar orbit (LEO, altitude ~550 km and inclination ~98°) using scientific instruments created at the SINP MSU.
Comparison of the results of the solar protons release times in solar proton events obtained by various methods
The comparison was made between the values of the solar release times of unrelativistic protons determined on scailing similarity time profiles of solar proton events and results of papers in which the solar release times of relativistic protons in GLE is determined on first observations with utilizing the method of velocity dispersion and on the first observations on neutron monitors with account of the dependence of the length of Sun–Earth magnetic line on solar wind velocity.
Review of study of submillimeter radiation from the Sun and astrophysical sources
We presented a brief overview of publications dedicated to observations of the Sun and other objects in the Universe in the submillimeter range of the electromagnetic spectrum. The main objective is to estimate the expected fluxes of solar flares in the terahertz range and to determine the classes of celestial bodies that could be potential sources of submillimeter waves. This data is necessary for developing scientific equipment that records spectral fluxes of terahertz radiation from astrophysical objects, with the aim of studying the mechanisms of energy release and acceleration of charged particles in the conditions of cosmic plasma.
Variations in characteristics of the northern hemisphere's middle atmosphere during solar proton events of January 2005
Characteristics of the middle atmosphere of the Northern hemisphere were investigated during Solar Proton Events of January 2005; the data of the MERRA-2 archive being used. It was found that the events under study were accompanied by sharp changes of zonal wind velocity and temperature in the high-latitudinal atmosphere. The obtained results provide evidence for an intensification of the stratospheric polar vortex during the studied events, which was followed by a sharp weakening of the vortex and the development of a small stratospheric warming.
Background of single muons at the Baksan underground scintillation telescope
The Baksan underground scintillation telescope is the sole detector in Russia dedicated to the observation of neutrinos from core-collapse supernovae. Candidates for neutrino events within the detector are identified as single triggers from individual counters. The background rate of single triggers from the internal planes is measured at 0.02 s–1. A methodology is proposed for investigating the background of penetrating atmospheric single muons, which is based on the development of a geometric model of the detector.
Search for neutrino events on the Baksan underground scintillation telescope in coincidence with gamma-ray bursts from Fermi GBM and Swift BAT
At the Baksan underground scintillation telescope, work is currently underway to organize a continuous search for multi-messenger events based on muon neutrinos registered by the facility. Gamma-ray bursts are one of the important components of such observations. By now, space gamma-ray telescopes have accumulated a significant amount of data. The facility data have been analyzed in coincidence with the gamma-ray burst catalogs from the Fermi Gamma-ray Burst Monitor and Swift Burst Alert Telescope instruments.
Zenith-angle dependence of local muon density spectra of extensive air shower near the horizon
The integral local muon density spectra (LMDS) of EAS at large zenith angles were reconstructed on the basis of the DECOR experimental data on muon bundles detected in a long-term measurement series from 03.05.2012 to 04.07.2023. The results were obtained for two threshold muon density values of 0.015 and 0.068 particles/m2, corresponding to the detection of bundles with a multiplicity of at least 3 and at least 5 muons in the detector. At zenith angles less than 80°, the zenith-angle dependence of LMDS is well described by a power function of the zenith angle cosine. However, with a further increase in the zenith angle, this dependence changes significantly, and at angles of 87–88°, the measured values exceed the specified simple extrapolation by about an order of magnitude. This is due to the inapplicability of the flat atmosphere approximation at such angles. A simple formula has been obtained that takes into account the curvature of the Earth's atmosphere.
Investigation of the extensive atmospheric showers spatial-temporal structure according to the Tunka-Grande array
We presented a study of extensive atmospheric showers with atypical spatial and temporal structure according to the data of the Tunka-Grande scintillation array. The events are considered, during which pulses with multi-peak structure and multi-pulse signals were observed in the detectors of the Tunka-Grande array.
Potential locations for the deployment of the full-scale TAIGA-100 gamma-ray observatory
We discussed possible locations for the deployment of the TAIGA-100 gamma-ray observatory with a hybrid detector system on an area of about 100 km2, which will make a significant contribution to solving many fundamental problems of cosmic ray physics and gamma-ray astronomy.
Differential sensitivity of the TAIGA-IACT facility in stereo observation mode
We evaluated the differential sensitivity of the 5 atmospheric Cherenkov telescopes under construction as part of the TAIGA astrophysical complex. The procedure of simulating of detected gamma-rays with energies from 2 to 200 TeV in the stereo observing mode is described, as well as the gamma-hadron separation technique used to determine the differential sensitivity of the facility.
Giant atmospheric showers detected by the Yakutsk extensive air showers array
The two most powerful extensive air showers (EAS) with energies of about 1020 eV, registered at the Yakutsk EAS array during the entire observation period of 1974–2024, are considered. Both showers hit the array near the center and triggered all surface detectors and underground muon detectors with a threshold energy of Eu = 1.0 · cos θ GeV. These events have an abnormally high fraction of muons, which is beyond current model predictions. This may change our understanding of hadron interactions at ultra-high energy, but there is also a possibility that these showers were initiated by some exotic primary particles.
Light component of cosmic rays' estimation in the range 200–10000 TeV by hybrid method
We presented new results on measuring the spectrum of the light component (protons + helium) of cosmic rays in the classical knee region in the primary cosmic rays' spectrum at an energy of ~ 200-20000, obtained from hybrid data of the TAIGA experiment. In hybrid method Cherenkov light created in atmosphere by extensive air showers is recorded simultaneously by two (IACT + HiSCORE) installations. At the same time, the separation of showers from the light component is carried out for the first time according to the image parameters recorded by the IACT atmospheric image telescope. The developed approach to the separation of the light component is based on and confirmed by Monte Carlo calculations. In the obtained spectrum of the light component in the energy range 200–20000 TeV, a pronounced feature is observed at an energy of about 3 PeV.
Iron nuclei ultra-high energy cosmic rays near the Earth
Assuming cosmic rays at ultra-high energies being of extragalactic origin we discuss propagation of cosmic iron nuclei with energies above 1019 eV from their sources to the Galaxy. In extragalactic space cosmic nuclei interact with background emissions and inevitably fragment. We analyze the fraction of iron nuclei reaching the Earth and its energy dependence on distances from cosmic ray sources. It is obtained that energies of iron nuclei can be used to find restriction on the distances from their sources.
Spectrum and composition of primary cosmic rays by the data of the TAIGA-HiSCORE array
The results of the operation of the TAIGA-HiSCORE array after increasing the number of stations to 114 and directing all stations to the zenith are presented. The conversion from the measured Cherenkov light flux of the extensive air shower (EAS) to the primary cosmic particle energy is refined. The ⟨ln A⟩ parameter, recalculated from the maximum depth, characterizing the average composition of primary cosmic radiation, is compared with the results obtained at our Tunka-133 installation, as well as with the results of the LHAASO and AUGER experiments.
Search for variations in the frequency of registration of delayed particles at the MSU extensive air showers array
At the MSU EAS array the temporal distributions of particles in extensive air showers (EAS) with energies greater than 1014 eV were studied. Delayed particles were registered in 3.5% of EAS. The flash in the frequency rate of registration of delayed particles from 1986 to 1990 with a maximum of the registration frequency in 1987 and the fine structure of which at the decline of the flash, consisted of a series of bursts of quasi-periodic fading oscillations with an oscillation period of approximately 4 days and a burst duration of about 32 days, is discussed. At the same time, the EAS frequency registration rate in limits of statistical errors was unchanged.
High-Energy Events Registration System of Space-Based Gamma-Ray Telescope
We present a description of the design and main results obtained from measurements with a prototype of the high-energy event registration system of the space-based gamma-ray telescope on the positron beam of the S-25R "Pakhra" synchrotron at the Lebedev Physical Institute of the Russian Academy of Sciences. The prototype includes an anticoincidence and time-of-flight systems, a pre-shower detector and a calorimeter based on BC-408, BGO and CsI(Tl) scintillators with appropriate front-end and processing electronics. Silicon photomultiplier matrices were used as photosensors in all scintillation detectors of the prototype.
Properties of GRBs high-energy gamma-emission according to Fermi/LAT, CORONAS-F/ABC-F and PHOTON/NATALYA-2M data
The AVS-F catalogue contains several tens of GRBs, the one of NATALYA-2M consists of 6 objects (maximum photon energy ∼150 and ∼60 MeV, respectively). The Fermi/LAT catalogue contains more than 200 bursts in the range E > 100 MeV. Different behavior of the prompt emission time profiles is observed in the high and low energy ranges during some events with the presence of a high-energy spectral component. When using the parameter Rt (the ratio of the arrival time of photon with maximum energy to the duration of the burst) that does not require taking into account cosmological duration dilation, the following groups are distinguished among long bursts: (1) for ∼25% of GRBs the duration of high-energy emission is shorter than that of low-energy range; (2) for the remaining ∼75% the opposite situation is observed, but the maximum energy γ is detected during the low-energy prompt emission (2a) or after its completion (2b). The characteristics of GRBs with γ in the sub-TeV region are similar to types 2a and 2b, there is no significant correlation between their maximum energy and redshift.
Spectra of protons and helium nuclei from tevatrons according to satellite experiments: indication to non-classical character of cosmic ray diffusion
Within the framework of the non-classical diffusion model created by the authors, an astrophysical interpretation is given of the results of precision measurements of the energy spectra of protons and helium nuclei obtained in the last decade in satellite experiments. It is shown that the breaks in the spectra in the TeV energy region, established in the DAMPE and CALET experiments, can be explained by considering the contributions from a group of tevatrons located at a distance of 150–200 pc from the Earth and having an age of ~ (4–6) · 105 years.
Experimental study of galactic cosmic ray fluxes in the solar modulation energy region
Proposals for a new approach to the development of scientific equipment for the study of galactic and solar cosmic ray fluxes in the solar modulation energy range (30–1000 MeV/nucleon) with elementary charge and mass resolution are considered. It is proposed to place the equipment on the Russian space station ROS (project "Modulation") and on the international scientific lunar station MNLS (project "Moon–Modulation"), if it is created. The projects assume the creation of a database of galactic and solar cosmic rays (SCR) for the entire solar activity cycle. Such a database is necessary to improve numerical models of the fluxes of energetic heliospheric particles in interplanetary and near-Earth space.
The characteristics of Forbush decreases based on data from AMS-02 experiment and fluxes of solar cosmic rays on GOES-15 one
An analysis of the dependence of the amplitudes of the 10 strongest preceded by Halo-type CMEs Forbush decreases in proton and helium nuclei fluxes according to AMS-02 data on the magnetic rigidity of particles showed that it is well approximated by a power function (as was shown in the PAMELA experiment) in the rigidity range from 1 to 10–12 GV. The index of this function is in the range from –0.38±0.02 to –0.68 ± 0.04 for protons and from –0.41± 0.03 to –0.79 ± 0.04 for helium nuclei. But in a wider range of rigidity values up to 20 GV, such approximation significance level is only 90–92% for protons and 90–96% for helium nuclei. Exponential functions providing 95–99% significance level both for protons and helium nuclei should be used over the entire range of rigidities. Comparison of time series for protons according to AMS-02 and GOES-15 data shows the possibility of observing SEP and SPE together with the background Forbush decreases.
Electromagnetic mechanism for formation of galactic cosmic rays’ anisotropy
We calculate the characteristics of the anisotropy of galactic cosmic rays formed by an electromagnetic mechanism. The mechanism is based on the combined action of the induction electric field and the regular magnetic field of the moving solar wind. For cosmic rays with an energy of 10 GeV, the following results were obtained: 1) vector anisotropy of 0.4 – 0.6% is directed perpendicular to the Earth-Sun line from west to east; 2) tensor anisotropy has the form of a biaxial ellipsoid, the minor axis of which is directed along the interplanetary magnetic field. The calculations correspond to the measurements.
Estimation of extensive air shower primary parameters using angular distribution of the Cherenkov light in the SPHERE-3 experiment
Some plans for the development of the SPHERE experiment are presented. Namely, reasons for the introduction of an additional detector of the angular distribution of Cherenkov light, pointed at zenith, are given. It can only work together with the main telescope but can yield important information on the primary particle direction and mass. Construction and capabilities of the detector are discussed, draft algorithms for direction definition are revealed, and sensitivity to the primary mass is shown.
A novel type of silicone rubber-based scintillator for extensive air showers particle detection
We proposed to use new inexpensive specialized scintillators optimized for different types of particles in experiments of detecting extensive air showers. The scintillators developed in our laboratory are based on locally produced phosphors immersed in a compound — optically transparent silicone rubber, so we called them "silicone rubber-based scintillators". Some of the first versions of such scintillators are already successfully used to register thermal neutrons and cascade particles in a number of Extensive Air Showers arrays created with our participation. We show here preliminary results of the development of specialized scintillators of this type to record different particles: fast neutrons, muons, electrons and gamma rays.