Yu. N. Mishutina

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.

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.

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.

Analysis of the anisotropy of the muon flux, according to data obtained by the URAGAN muon hodoscope during heliospheric disturbances

Features of studying heliospheric disturbances caused by changes in the parameters of the interplanetary magnetic field by the anisotropy of the muon flux of cosmic rays detected on the surface of the Earth by the URAGAN muon hodoscope are considered. The anisotropy of the muon flux in the period 2007–2011 is analyzed. The forecasting potential of our approaches to studying heliospheric disturbances using the penetrating component of cosmic rays is evaluated.

Local anisotropy of muon flux during Forbush decreases from URAGAN data

The approach to the analysis of spatial-angular characteristics of the muon flux variations at different phases of Forbush decrease development according to the muon snapshots (muongraphies) obtained using muon hodoscope URAGAN, as well as the analysis results are presented.

Real-time experimental data of the muon hodoscope URAGAN accessible in www

Muon hodoscope URAGAN consists of four independent supermodules with total area 46 m2 and is under operation in the Experimental complex NEVOD (MEPhI, Moscow) from 2007. At present, the sequence of real-time data of angular variations of muon flux measured in the hodoscopic mode and also the results of their analysis: local angular anisotropy, wavelet frequencies, etc. are available at the URAGAN web-site. Some peculiarities of application of these data for the analysis of various events in heliosphere, magnetosphere and atmosphere are discussed.

Temperature effect corrections for URAGAN based on CAO, GDAS, NOAA data

For the analysis of muon flux variations caused by extra-atmospheric processes it is necessary to introduce corrections for meteorological effects. For temperature effect (TE) correction it is necessary to know the temperature profile of the atmosphere. As a rule, this profile is measured by meteorological balloons two or four times a day. Alternative sources are satellite observations and data obtained from models of atmosphere used for weather forecasting. Vertical temperature profiles obtained from NOAA satellites, GDAS (Global Data Assimilation System) and CAO data (Central Aerological Observatory, Russia) for standard isobaric levels were compared. Mean value of temperature difference for most levels does not exceed 1 K. Comparison of URAGAN data corrected for TE with CAO information, satellites and GDAS shows a good agreement. Counting rate and anisotropy of the muon flux corrected for meteorological effects for 2007-2014 are presented.

Real-time data of the URAGAN muon hodoscope

Data from detectors deployed on space satellites and on the surface of the Earth are used to monitor space weather. One such detector is the URAGAN muon hodoscope, which registers the angular distribution of the muon flux in a wide range of zenith angles. The results from processing data in the real-time mode are time series of characteristics of angular distributions. Images of the current plots of time series and matrices of variations of angular distributions can be seen at the NEVOD experimental complex’s website on the Internet.