E. I. Yakovleva

Specific features of studying Forbush decreases in the muon flux

The variations in the cosmic ray (CR) muon flux during the Forbush decreases (FDs), registered by the DECOR muon detector and the URAGAN muon hodoscope during the periods of their operation from 2004 to 2006, are analyzed. The unified method for determining the parameters of variations in the CR flux during FDs has been developed, and the dependences of the FD characteristics on the rigidity of primary CRs and information about the spatial-angular dynamics of the muon flux during FDs have been obtained.

Investigating the energy, angular, and temporal characteristics of forbush effects registered by the URAGAN muon hodoscope

The results from analyzing variations in the flux of cosmic ray muons during Forbush effects (FEs) registered by the URAGAN muon hodoscope over the period 2005–2009 are presented. The dependences of the amplitudes for reductions in the intensity of the cosmic ray muon flux on the energy of primary particles in energy ranges higher than 10 GeV were obtained. Their changes upon different phases of Forbush effect development were investigated. The local anisotropy vectors were calculated on the basis of spatial-angular variations in the muon flux. Correlations between the parameters of physical properties in the near heloiosphere related to the Forbush effects and the characteristics of muon flux variations were analyzed.

Coupling functions for muon hodoscopes

The specific features of calculating the coupling functions for muon hodoscopes are considered. The results of calculating the main coupling functions for three versions of the primary spectra of cosmic rays (CR)—galactic CR, solar CR during proton events, and galactic CR variations during Forbush decreases-are presented. The calculations have been performed based on modeling CR propagation through the Earth’s atmosphere using the CORSIKA code. The mean and median CR energies, contributing to the muon detector counting rate, have been calculated for different zenith angles. It has been shown that muon detectors are sensitive to different energies of primary CRs for different directions.

Study of heliospheric disturbances on the basis of cosmic ray muon flux anisotropy

The features of the study of heliospheric disturbances on the basis of ground level cosmic ray muon flux observations are discussed. The muon hodoscope URAGAN simultaneously detects muons from various directions of the celestial hemisphere. This allows us to analyze spatial-angular variations of muon flux during such events. Heliospheric disturbances that caused the changes of interplanetary magnetic field parameters measured by various space vehicles are considered. A special attention is paid to the analysis of the response of the muon hodoscope URAGAN for recent most powerful solar flares that occurred in March 2012. In accordance with the results of the study, methods of separating main heliospheric disturbances are proposed. The prognostic potential of the developed approaches to the study of heliospheric disturbances by means of the penetrating component of cosmic rays is evaluated.

Present status of muon diagnostics

Muon diagnostics is a technique of remote monitoring of various dynamic processes in the heliosphere, the magnetosphere and the atmosphere of the Earth based on the analysis of spatial-angular and temporal variations of muon flux simultaneously detected from all directions of the upper hemisphere. The developed approaches to data analysis and results of the study of various terrestrial and extra-terrestrial processes detected by means of a wide aperture URAGAN muon hodoscope are discussed.

Forbush decreases recorded by the URAGAN muon hodoscope in 2006–2011

Variations in the cosmic ray muon flux on Earth’s surface during Forbush decreases (FD) recorded by the URAGAN muon hodoscope in 2006–2011 are investigated. The dependence of the rate of amplitude reduction on the primary particle energy in a range above 10 GeV at different phases of FD development is studied by analyzing the variations in the cosmic ray muon flux recorded with the hodoscope. Analytical data on the spatial and angular dynamics of the muon flux are used to estimate variations in the spatial anisotropy of the muon flux during FDs.

Investigating the albedo muon flux at the NEVOD-DECOR experimental complex

New results from investigating the flux of atmospheric muons scattered from the ground to the upper hemisphere, obtained with the NEVOD-DECOR experimental complex from December 2011 to March 2013, are presented.

Correcting data from the URAGAN muon hodoscope for the temperature profile of the atmosphere, using data from the CAO, GDAS, and ALISA-SK receiving station for 2007–2014

In order to analyze muon flux variations caused by extra-atmospheric processes, it is necessary to introduce corrections for meteorological effects. To take the temperature effect into account, we must know the temperature profile of the atmosphere. Vertical temperature profiles obtained from NOAA satellites and calculated using the model of the Global Data Assimilation System (GDAS) are compared to data from the Central Aerological Observatory (CAO, Dolgoprudny) for standard isobaric levels. The average temperature difference for most levels does not exceed 1 K. A comparison of the data from the URAGAN hodoscope, corrected for the temperature effect using data from the CAO, NOAA, and GDAS, shows excellent mutual agreement. A series of integral time counting rate and the anisotropy of the muon flux for 2007–2014, corrected for atmospheric effects, are presented.

Study of temporal changes of Forbush decrease amplitude spectra for different types of heliospheric disturbances

Experimentally obtained temporal changes of the index of the Forbush decreases amplitude spectrum, caused by heliospheric disturbances of different types at different phases of 23rd and 24th solar cycles and recorded by the URAGAN muon hodoscope, are studied. Coupling functions of the primary and the secondary cosmic ray fluxes for five zenith-angular intervals are used to obtain the energy spectrum of Forbush decrease amplitudes in a flux of muons. Analysis of the energy characteristics is based on the dependence of the amplitude of the decrease in the intensity of cosmic ray muons on the mean log energy of the primary particles that contribute to changes in the count rate of the URAGAN muon hodoscope during Forbush decreases.

Study of characteristics of Forbush decreases detected in 2006 ? 2011 by means of muon hodoscope URAGAN

Results of the study of variations of cosmic ray muon flux at the Earth surface during Forbush decreases (FD) registered in 2006 – 2011 by means of muon hodoscope URAGAN both for the integral counting rate and for different angular intervals are presented. Dependences of the amplitude of the decrease of cosmic ray muon intensity on the energy of primary particles in the energy region above 10 GeV during different phases of the FD were obtained. On the basis of the analysis of spatial-angular distribution of muon flux, values of the horizontal projections of the local anisotropy vector were calculated and their dynamics was studied. Energy, angular and temporal characteristics of Forbush decreases determined from cosmic ray muon data are compared with basic parameters characterizing conditions of near-Earth space before and during FD.