A new method for studying cosmic ray anisotropy by means of muon bundle detection at the Earth’s surface is described. An important advantage of this method is a simple way to compensate the atmospheric effects in the counting rate of muon bundles. Seasonal and diurnal variations of the muon bundle counting rate are almost completely eliminated by using only one atmospheric parameter. For the first time, the muon multiplicity in the detected bundles was used to estimate the dependence of the anisotropy amplitude on the primary energy. Parameters of the cosmic ray dipole anisotropy were obtained for two average logarithmic values of primary energies of 1 and 5 PeV.

Flicker noise spectroscopy is developed for the remote identification of processes of powerful solar activity in the form of coronal mass ejections (CMEs) directed toward the Earth. Results are presented from analyzing geo-effective events (>G1) using data from the international network of neutron monitors and the URAGAN multidirectional muon hodoscope that indicate the emergence of precursors (1–2 days in advance) of CMEs approaching the Earth’s orbit.

From the data (uncorrected for temperature effect) of the global network of neutron monitors (GNNM), along with the data of the Yakutsk muon telescope suite and the URAGAN muon hodoscope (Moscow), we applied a modified spectrographic global survey (SGS) for the 2018 Aug event to split cosmic ray variations into components of primary, magnetospheric, and atmospheric origin. Obtained were the time evolutions for the different-rigidity primary particle isotropic flux, pitch-angle anisotropy of cosmic rays (CRs), and interplanetary magnetic field (IMF) orientation. We provide variations in the rigidity of the geomagnetic cutoff (RGC) in Irkutsk and in the average bulk temperature at the points that observe charged components.

The recognition of local anisotropies of muon fluxes using the functions of normalized variations for matrix observations of the URAGAN hodoscope is considered. Normalized instrument functions are introduced and spatiotemporal filtration is used, which become the basis of computation of the functions of normalized variations. An algorithm of recognition of local anisotropies is implemented. An experimental study of the application of the functions of normalized variations is carried out that confirms the efficiency of the developed algorithm for recognition of local anisotropies of muon fluxes in times series of matrix observations of the URAGAN hodoscope.

Parameters of extensive air showers detected by the facilities of the NEVOD Experimental Complex are analyzed and compared with events simulated. The calibration and energy threshold of the NEVOD-EAS detector are discussed, as well as the results of retrieval of the axis directions from the NEVOD-EAS and DECOR data. An example of the event detected by all facilities of the complex is given.

From ground-based observations of cosmic rays (CR) at the global network of neutron monitors, Yakutsk suite of muon telescopes, and the URAGAN muon hodoscope (Moscow), through the modified method of the spectrographic global survey we investigated variations in CR of magnetospheric and atmospheric origin for September, 2017. We demonstrated the possibility to use the data on the unstable charged component of secondary CRs for the study of CR variations without the need to introduce corrections for temperature effect. Obtained were temporal variations in the planetary system of the CR rigidities of geomagnetic cutoff (RGC) and in the mass average air temperature at the points of observation of the charged components. Based on the data on the RGC planetary system variations within the axisymmetric model for the Earth bounded magnetosphere, we calculated the parameters for some magnetospheric current systems during the 2017 September geomagnetic disturbances.

In this paper we discuss the calibration of the NEVOD-EAS array which is a part of the Experimental Complex NEVOD, as well as the results of studying the response features of its scintillation detectors. We present the results of the detectors energy calibration, performed by comparing their response to different types of particles obtained experimentally and simulated with the Geant4 software package, as well as of the measurements of their timing resolution. We also discuss the results of studies of the light collection non-uniformity of the NEVOD-EAS detectors and of the accuracy of air-shower arrival direction reconstruction, which have been performed using other facilities of the Experimental Complex NEVOD: the muon hodoscope URAGAN and the muon tracking detector DECOR.

In this work, we use muon bundles, which are formed in extensive air showers and detected at the ground level, as a tool for searching for anisotropy in high-energy cosmic rays. Such choice is explained by the penetrating ability of muons that allows them to retain the direction of primary particles with good accuracy. In 2012–2022, we performed long-term muon-bundle detection with the coordinate-tracking detector DECOR, which is a part of the Experimental Complex NEVOD (MEPhI, Moscow). To search for cosmic-ray anisotropy, muon bundles arriving at zenith angles in the range from 15° to 75° in the local coordinate system are used. During the entire period of data taking, about 14 million of such events have been accumulated. In this paper, we describe some methods developed in the Experimental Complex NEVOD and implemented in our research, including: the method for compensating for the influence of meteorological conditions on the intensity of muon bundles at the Earth’s surface, the method for accounting for the design features of the detector and the inhomogeneity of the detection efficiency for different directions, as well as the method for estimating the primary energies of cosmic rays. Here we present the results of the search for the dipole anisotropy of cosmic rays with energies in the PeV region and also compare them with the results obtained at other scientific facilities.

A method for predicting geomagnetic storms based on the neural network digital processing of joint observations of the URAGAN muon hodoscope and the international system of neutron monitor stations has been proposed. A time series of Dst indices are used. Formulas for extrapolating model estimates of Dst indices have been developed. A fully-connected feed-forward neural network has been used. Prediction decision rule has been implemented. The probability characteristics of geomagnetic storm prediction have been estimated. An experimental study of the prediction method confirmed its effectiveness. It has been shown that the observations of the hodoscope–monitor system increased the probability of correctly predicting geomagnetic storms compared to using each of the observations separately.

Indicator matrices are proposed for the recognition of local anisotropies (LAs) of muon fluxes in time series of matrix observations of the URAGAN hodoscope. Reference and current time intervals are implemented, and confidence intervals are calculated for the mathematical expectations of Poisson observations in these intervals. An anomaly function is formed. Indicator matrices are obtained by comparing the anomaly functions with thresholds. The recognition of local anisotropies by indicator matrices and the decision-making procedure are tested on model and experimental observations. The efficiency of the application of indicator matrices for the recognition of LAs of muon fluxes (MFs) in time series of matrix observations of the URAGAN hodoscope is confirmed.

Muon hodoscope URAGAN (MEPhI, Moscow) with an area of 45 sq. m is capable of real time detection of the tracks of all muons arriving from the upper celestial hemisphere with a high spatial and angular accuracy (1 cm and 1 degree, respectively). The measured angular distribution of the muons flux over a certain period of exposure time and expressed in R.M.S. deviations from an averaged reference matrix and corrected for barometric and temperature effects represents a matrix-muonograph (by analogy with X-ray radiography) of the Earth's atmosphere and near-terrestrial space. Such muonograph contains information on the current variation the flux of cosmic muons associated with modulation processes in the heliosphere, magnetosphere and atmosphere of the Earth. The sequence of muonographs converted to the GSE coordinate system allows one to study in real time the dynamics of cosmic ray anisotropy and to identify in advance geoeffective processes in the heliosphere associated with solar activity. Results of the analysis of the anisotropy of the cosmic ray muon flux at the minima of the 23rd (2009-2010) and 24th (2018-2019) solar cycles are discussed.

Muon flux intensity modulation (MFIM) recognition is a relevant solar-terrestrial physics problem. The considered MFIM, recorded on the Earth's surface, are caused by extreme heliospheric events – the geoeffective solar coronal mass ejections. The URAGAN muon hodoscope (MH), developed by NRNU MEPhI, a computerized device that measures the intensities of muon fluxes, is used. In the MH, the number of muons falling per unit time on the MH aperture is calculated for the selected system of zenith and azimuthal angles. MH matrix data time series are formed. In the MH data, there are angular modulations due to the action of the hardware function HF, temporal modulations due to atmospheric disturbances and noise: the values of these modulations significantly exceed the values of MFIM of cosmic origin. This circumstance prevents effective MFIM recognition. A method for MFIM recognition is proposed, based on the mathematical apparatus of the introduced normalized variation functions for MH matrix data, and focused on overcoming the noted circumstance. A two-dimensional normalized HF is defined for MH. A quite realistic hypothesis is accepted about the initialiy uniform muon flux intensity distributions on a small reference time interval, where there are no extreme heliospheric events and the corresponding reference MH data do not contain significant MFIMs. The estimation of the two-dimensional normalized HF is carried out on the basis of a multiparameter model and its optimization fit to the reference MH data. In order to reduce noise errors, the estimate of the two-dimensional normalized HF is subjected to two-dimensional filtering and subsequent threshold filtering. Two-dimensional functions of variations of matrix MH datas with respect to two-dimensional normalized AF are calculated. The normalized variation functions are calculated by dividing the two-dimensional functions of variations of matrix MH data by the two-dimensional normalized HF. MFIM recognition method was tested on model and experimental MH data. A time series of model matrix MH data containing model MFIM was generated. Testing led to a conclusion that it is possible to recognize MFIM with decreases of about 2-3%. A time series of experimental matrix MH data was generated, in which the model MFIM-containing areas were made. Testing led to a conclusion that it is possible to recognize MFIM with the magnitudes of the decreases almost commensurate with the decreases for the case of model MH data. The proposed MFIM recognition method based on the normalized variation functions for matrix MH data has a favorable perspective for its application in solving problems of geomagnetic storm early diagnostics.

An analysis is performed of the diurnal variation in cosmic-ray muons measured with the URAGAN muon hodoscope from 2007 to 2019. Characteristics are given of the yearly average diurnal variation in the count rate in several zenith-angle intervals. The results are compared to the diurnal variations in the count rate of neutrons from ten neutron monitors.

Problems of digital processing of Poisson-distributed data time series from various counters of radiation particles, photons, slow neutrons etc. are relevant for experimental physics and measuring technology. A low-pass filtering method for normalized Poisson-distributed data time series is proposed. A digital quasi-Gaussian filter is designed, with a finite impulse response and non-negative weights. The quasi-Gaussian filter synthesis is implemented using the technology of stochastic global minimization and modification of the annealing simulation algorithm. The results of testing the filtering method and the quasi-Gaussian filter on model and experimental normalized Poisson data from the URAGAN muon hodoscope, that have confirmed their effectiveness, are presented.

The effect meteorological parameters have on the concentration of thermal neutrons is studied using data from the NEUTRON setup in the period May 2015 to February 2019. Daily and seasonal variations in the neutron count rate are obtained. Such variations are associated with changes in temperature. The effect the depth of the snow cover has on the neutron count rate for four winter periods is estimated. It is shown that meteorological parameters have a considerable impact on the concentration of neutrons near the surface. The total contribution from pressure, temperature, and the depth of the snow cover can be more than 30%.

The Experimental Complex (EC) NEVOD includes a number of detectors used to carry out basic research of cosmic rays (CR) and their interactions in the energy range 1011–1019 eV and applied research of the heliosphere, magnetosphere and atmosphere of the Earth by the muonography method which is based on the analysis of spatial-angular variations of the muon flux generated by primary CR particles with energies of 10^9–10^11 eV. The EC NEVOD is being constantly developed. Nowadays, it consists of three basic groups of experimental facilities unique in the world: the major facilities (Cherenkov water detector NEVOD, calibration telescope system — CTS, coordinate-tracking detector DECOR), the peripheral facilities (extensive air shower array NEVOD-EAS, distributed thermal neutron detector systems PRISMA and URAN), the muon hodoscopes for cosmophysical and geophysical investigations (TEMP and URAGAN). All detectors and installations of the first two groups are combined by a multilevel triggering system and the time synchronization system ensuring timestamping of registered multicomponent events. Today, the Experimental Complex NEVOD is the only facility capable of studying such a wide set of fundamental and applied scientific problems in the field of cosmic rays and solar-terrestrial physics.