Michael V. Alania

Features of the solar wind large-scale structure in the different periods of solar activity based on the variations of cosmic rays

The relations between the energy spectrum exponent γ of cosmic ray isotropic intensity variations (δD(R)D (R) ∝ R−γ) and the parameter α which characterizes the diffusion coefficients χ dependence on the cosmic ray particles rigidity R (χ∝Rα) has shown (α ∝ γ). The large-scale structural changes of the magnetic inhomogeneities of solar wind in the different periods of solar activity is the general mechanism of 11-year variations of cosmic rays above energy 1–2 GeV. The energy spectrum exponent γ of cosmic ray isotropic intensity variations can be considered as a important tool for the investigation of the temporal and spatial changes of the large-scale fluctuations in the interplanetary magnetic field strength.

On the influence of solar activity and the solar magnetic field on the 27-day variation of galactic cosmic rays

The calculated amplitude of the 27-day variation using super neutron monitors data has been compared with changes of the distribution of solar activity on the Sun. Close correlation of the two-peaked pattern of the galactic cosmic rays 27-day variation with changes of the longitudinal asymmetry of the sunspot distribution at the maxima epochs of solar activity has been observed. It is reasonable to assume that drastic changes of the longitudinal asymmetry of solar activity near the solar maximum are reflected in the perturbation of the heliospheric structure, causing the depression of the 27-day modulation. Marked differences between the Suns magnetic polarity cycles, qA > 0 and qA 0 and qA 0 than in the qA < 0 solar magnetic cycles being in good agreement with the experimental data for the minima epochs of solar activity.

On the Relationship of the 27-day Variations of the Solar Wind Velocity and Galactic Cosmic Ray Intensity in Minimum Epoch of Solar Activity

We study the relationship of the 27-day variations of the galactic cosmic ray intensity with similar variations of the solar wind velocity and the interplanetary magnetic field based on observational data for the Bartels rotation period # 2379 of 23 November 2007 – 19 December 2007. We develop a three-dimensional (3-D) model of the 27-day variation of galactic cosmic ray intensity based on the heliolongitudinally dependent solar wind velocity. A consistent, divergence-free interplanetary magnetic field is derived by solving Maxwell’s equations with a heliolongitudinally dependent 27-day variation of the solar wind velocity reproducing in situ observations. We consider two types of 3-D models of the 27-day variation of galactic cosmic ray intensity, i) with a plane heliospheric neutral sheet, and ii) with the sector structure of the interplanetary magnetic field. The theoretical calculations show that the sector structure does not significantly influence the 27-day variation of galactic cosmic ray intensity, as had been shown before, based on observational data. Furthermore, good agreement is found between the time profiles of the theoretically expected and experimentally obtained first harmonic waves of the 27-day variation of the galactic cosmic ray intensity (with a correlation coefficient of 0.98±0.02). The expected 27-day variation of the galactic cosmic ray intensity is inversely correlated with the modulation parameter ζ (with a correlation coefficient of −0.91±0.05), which is proportional to the product of the solar wind velocity V and the strength of the interplanetary magnetic field B (ζ∼VB). The high anticorrelation between these quantities indicates that the predicted 27-day variation of the galactic cosmic ray intensity mainly is caused by this basic modulation effect.

27-Day variations of galactic cosmic rays and changes of solar and geomagnetic activities

Abstract Neutron monitor, solar and geomagnetic activity data have been used to investigate variations of galactic cosmic ray intensity connected with the Suns rotation for different epochs of solar activity. Behaviors of longitudinal asymmetry of the sunspot distribution, coronal line emission and tilt angles of the heliospheric neutral sheet have been studied. A relationship of the temporal changes of the amplitudes of the 27-day variations of galactic cosmic rays and Kp index of geomagnetic activity with the tilt angles of the heliospheric neutral sheet have been investigated. It is shown that there are no any noticeable relationship between the amplitudes of the 27-day variations of galactic cosmic rays and the tilt angles of the heliospheric neutral sheet for both of the qA > 0 and the qA 0 cycle than for the qA

The 27-Day Cosmic Ray Intensity Variations During Solar Minimum 23/24

We have studied the 27-day variations and their harmonics of the galactic cosmic ray (GCR) intensity, solar wind velocity, and interplanetary magnetic field (IMF) components in the recent prolonged solar minimum 23 24. The time evolution of the quasi-periodicity in these parameters connected with the Suns rotation reveals that their synodic period is stable and is aprox 26-27 days. This means that the changes in the solar wind speed and IMF are related to the Suns near equatorial regions in considering the differential rotation of the Sun. However, the solar wind parameters observed near the Earths orbit provide only the conditions in the limited local vicinity of the equatorial region in the heliosphere (within in latitude). We also demonstrate that the observed period of the GCR intensity connected with the Suns rotation increased up to aprox 33-36 days in 2009. This means that the process driving the 27-day variations of the GCR intensity takes place not only in the limited local surroundings of the equatorial region but in the global 3-D space of the heliosphere, covering also higher latitude regions. A relatively long period ( aprox 34 days) found for 2009 in the GCR intensity gives possible evidence of the onset of cycle 24 due to active regions at higher latitudes and rotating slowly because of the Suns differential rotation. We also discuss the effect of differential rotation on the theoretical model of the 27-day variations of the GCR intensity.

Dependence of the 27-day variation of cosmic rays on the global magnetic field of the Sun

We show that the higher range of the heliolongitudinal asymmetry of the solar wind speed in the positive polarity period (A > 0) than in the negative polarity period (A 0) than in 1985–1987 (A < 0). Subsequently, different ranges of the heliolongitudinal asymmetry of the solar wind speed jointly with equally important corresponding drift effect are general causes of the polarity dependence of the amplitudes of the 27-day variation of the GCR intensity. At the same time, we show that the polarity dependence is feeble for the last unusual minimum epoch of solar activity 2007–2009 (A < 0); the amplitude of the 27-day variation of the GCR intensity shows only a tendency of the polarity dependence. We present a three dimensional (3-D) model of the 27-day variation of GCR based on the Parker’s transport equation. In the 3-D model is implemented a longitudinal variation of the solar wind speed reproducing in situ measurements and corresponding divergence-free interplanetary magnetic field (IMF) derived from the Maxwell’s equations. We show that results of the proposed 3-D modeling of the 27-day variation of GCR intensity for different polarities of the solar magnetic cycle are in good agreement with the neutron monitors experimental data. To reach a compatibility of the theoretical modeling with observations for the last minimum epoch of solar activity 2007–2009 (A < 0) a parallel diffusion coefficient was increased by ∼40%.

Peculiarities of cosmic ray modulation in the solar minimum 23/24

We study changes of the galactic cosmic ray (GCR) intensity for the ending period of the solar cycle 23 and the beginning of the solar cycle 24 using neutron monitors experimental data. We show that an increase of the GCR intensity in 2009 is generally related with decrease of the solar wind velocity U, the strength B of the interplanetary magnetic field (IMF), and the drift in negative (Aneg) polarity epoch. We present that temporal changes of rigidity dependence of the GCR intensity variation before reaching maximum level in 2009 and after it, do not noticeably differ from each other. The rigidity spectrum of the GCR intensity variations calculated based on neutron monitors data (for rigidities greaten than 10 GV) is hard in the minimum and near minimum epoch. We do not recognize any non-ordinary changes in the physical mechanism of modulation of the GCR intensity in the rigidity range of GCR particles to which neutron monitors respond. We compose 2-D non stationary model of transport equation to describe variations of the GCR intensity for 1996-2012 including the Apos (1996-2001) and the Aneg (2002-2012) periods; diffusion coefficient of cosmic rays for rigidity 10-15 GV is increased by 30 percent in 2009 (Aneg) comparing with 1996 (Apos). We believe that the proposed model is relatively realistic and obtained results are satisfactorily compatible with neutron monitors data.

Experimental and theoretical investigations of the 11-year variation of galactic cosmic rays

Data of super neutron monitors have been used to study features of the temporal changes of the energy spectrum of the galactic cosmic rays isotropic intensity variations in the various ascending and descending epochs of solar activity (1954–2000) for different solar magnetic cycles (qA > 0 and the qA < 0). Parkers transport equation is numerically solved in order to establish a relationship between the experimentally obtained and theoretically expected energy spectra of.galactic cosmic rays. It is found that the theoretical expected energy spectrum is single valued determined by the dependence of the diffusion coefficient on the rigidity of galactic cosmic rays. The temporal changes of the energy spectrum of galactic cosmic rays isotropic intensity variations from the maxima to the minima epochs of solar activity indicate the radical redistributions of the EAFs fluctuations (irregularities) from the higher frequencies to the lower frequencies. It is concluded that this radical redistributions of the DVIFs fluctuations from the maxima to the minima epochs is one of the general reasons (mechanism) of the 11-year variation of the galactic cosmic rays m 2003 COSPAR.

The role of drift on the diurnal anisotropy and on temporal changes in the energy spectra of the 11-year variation for galactic cosmic rays

Neutron monitor and interplanetary magnetic field data have been used to study features of the role of drift effect in the temporal changes of the diurnal anisotropy and of the energy spectrum of the 11-year variation of galactic cosmic rays. In order to strictly separate the sectors of the interplanetary magnetic field and its influence on the anisotropy of galactic cosmic rays four solar minima periods (1965, 1976, 1987 and 1997) have been considered. An attempt to separate drift effects in the diurnal anisotropy of galactic cosmic rays, first, due to the gradient and curvature of the regular interplanetary magnetic field, and second, due to the heliospheric neutral sheet has been made. The global survey methods has been used to calculate the components of the three dimensional diurnal anisotropy of galactic cosmic rays based on neutron monitors data. It is shown that there are significant differences between the diurnal anisotropy of galactic cosmic rays found in the reliably established various sectors (duration of each sectors is ≥ 4 days) of the interplanetary magnetic field. The interplanetary magnetic field sector structure effect in the diurnal anisotropy of galactic cosmic rays is assumed to be connected to the heliospheric neutral sheet drift, while 22-year variation of the diurnal anisotropy of galactic cosmic rays is assumed to be connected to drift due to the gradient and curvature of the regular interplanetary magnetic field for different qa > 0 and qA 0 and the qA<0 solar magnetic cycles. The temporal changes of the exponent index of the 11-year variation of GCR generally is connected with the various character of the diffusion in interplanetary space for minima and maxima epochs of solar activity.

Statistical analyses of influence of solar and geomagnetic activities on car accident events

Statistical analyses of the influence of Solar and geomagnetic activity, sector structure of the interplanetary magnetic field and galactic cosmic ray Forbush effects on car accident events in Poland for the period of 1990-1999 have been carried out. Using auto-correlation, cross-correlation, spectral analyses and superposition epochs methods it has been shown that there are separate periods when car accident events have direct correlation with Ap index of the geomagnetic activity, sector structure of the interplanetary magnetic field and Forbush decreases of galactic cosmic rays. Nevertheless, the single-valued direct correlation is not possible to reveal for the whole period of 1990-1999. Periodicity of 7 days and its second harmonic (3.5 days) has been reliably revealed in the car accident events data in Poland for the each year of the period 1990-1999. It is shown that the maximum car accident events take place in Poland on Friday and practically does not depend on the level of solar and geomagnetic activities.