Analysis of Muon Flux Variations Caused by High-Speed Solar Wind During Periods of Low Solar Activity
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ELEMENTARY PARTICLES AND FIELDS Experiment
Analysis of Muon Flux Variations Caused by High-Speed Solar Wind During Periods of Low Solar Activity A. Yu. Konovalova1)* , I. I. Astapov1) , N. S. Barbashina1), N. V. Osetrova1), Y. N. Mishutina1), V. V. Shutenko1), and I. I. Yashin1) Received July 29, 2019; revised July 29, 2019; accepted July 29, 2019
Abstract—The influence of a high-speed solar wind on the state of magnetosphere, as well as on the cosmic ray flux registered on the Earth’s surface by the muon hodoscope URAGAN (MEPhI) is discussed. The results of the analysis of the parameters of muon flux local anisotropy in the periods of low solar activity (2008–2009 and 2017–2018) during geomagnetic disturbances caused by the high-speed solar wind are presented. DOI: 10.1134/S1063778819660311
1. INTRODUCTION The strongest disturbances in the heliosphere and magnetosphere are caused by coronal mass ejections. However, an important role is also played by recurrent processes associated with high-speed fluxes of the solar wind (SW) generated in coronal holes in the Sun. As a rule, such processes are the main source of magnetic disturbances on the Earth during periods of low solar activity. These disturbances have a direct impact on the fluxes of primary cosmic rays penetrating the interplanetary space. Interacting with the magnetic field inhomogeneities in the solar wind, these fluxes are modulated. Muons preserve quite well the direction of primary cosmic-ray particles and therefore contain information about active heliosheric processes related to the solar activity [1]. 2. MUON HODOSCOPE URAGAN AND EXPERIMENTAL DATA The muon hodoscope (MH) URAGAN is a wideaperture coordinate-tracking detector operating in the Scientific and Educational Center NEVOD (MEPhI, Moscow). The MH URAGAN allows simultaneous registration of muons arriving from any direction of the upper hemisphere within the detector aperture and is used to study the characteristics of muon flux variations as a function of the spatial angle [2]. To study two-dimensional variations of the muon flux registered with the muon hodoscope URAGAN, 1)
National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Moscow, 115409 Russia. * E-mail: [email protected]
the vector of the muon flux local anisotropy A is used. This vector is a sum of the unit vectors of the reconstructed tracks of individual muons normalized to the number of muons. The projections of the anisotropy vector in the local coordinate system are calculated by the following formulas: 1 Ma cos ϕ sin θ, (1) AX = N ϕ θ 1 Ma sin ϕ sin θ, AY = N ϕ θ
AS = AX cos ϕ + AY sin ϕ0, AE = −AX sin ϕ + AY cos ϕ0, 1 cor Ma cosθ, AZ = cor N ϕ θ A = A2S + A2E + A2Z , where Ma is the matrix of the angular distribution of the muon flux; AX and AY are projections of vector A in the laboratory coordinate system; AS is a projection to the geographic axis South–North; AE is a projection to the axis East–West; AZ is a vertical projection; ϕ0 = 34.726◦ is an azimuthal angle between local and geographi
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