We ascribe this finding to the alternation of the sizes of the modulation regions of the 27-day variation of the GCR intensity in different epochs of solar activity. We show that the rigidity spectrum of the third harmonic (9 days) of the 27-day variation of the GCR intensity changes in a similar way as the spectra of the first and second harmonics, being hard in the maximum epochs and soft in the minimum epochs of solar activity. We study temporal changes of the rigidity (R) spectrum of the harmonics of the 27-day variation of the galactic cosmic ray (GCR) intensity using neutron monitors (NM) data for the period 1965–2002. An interesting feature of their solutions is that at distances of a few AU from the Sun (the exact distance depends on the parameter values), the phase of the 22-year variation with respect to A may reverse, so that larger variations are seen when A 0 minima, though future Ulysses results may provide information on conditions in this distance range when A < 0. Gil and Alania (2001) have obtained solutions to a 3-dimensional transport equation including drifts that with certain choices of the parameters assumed in the equation, can produce a larger 22-year variation in the cosmic ray density at Earth in A > 0 epochs. Thus, in the context of the model results, a simple displacement of the current sheet does not appear to be able to account fully for the 22-year variation. Parallel diffusion coefficient was increased by 40 percent Observations for the last minimum epoch of solar activity 2007-2009 (Aneg) a To reach a compatibility of the theoretical modeling with Of the solar magnetic cycle are in good agreement with the neutron monitorsĮxperimental data. We show that results of the proposedģ-D modeling of the 27-day variation of GCR intensity for different polarities (IMF) derived from the Maxwells equations. Measurements and corresponding divergence-free interplanetary magnetic field In the 3-D model is implementedĪ longitudinal variation of the solar wind speed reproducing in situ Of GCR based on the Parkers transport equation. We present a three dimensional (3-D) model of the 27-day variation Unusual minimum epoch of solar activity 2007-2009 (Aneg) the amplitude of theĢ7-day variation of the GCR intensity shows only a tendency of the polarityĭependence.
The same time, we show that the polarity dependence is feeble for the last Important corresponding drift effect are general causes of the polarityĭependence of the amplitudes of the 27-day variation of the GCR intensity. The heliolongitudinal asymmetry of the solar wind speed jointly with equally Period (Aneg) is one of the important reasons of the larger amplitudes of theĢ7-day variation of the galactic cosmic ray (GCR) intensity in the period ofġ995-1997 (Apos) than in 1985-1987 (Aneg).
Wind speed in the positive polarity period (Apos) than in the negative polarity We show that the higher range of the heliolongitudinal asymmetry of the solar Modeling of the 27-day variation of galactic cosmic ray (GCR) intensity is of interest since Richardson, Cane and Wibberenz (1999) found that the recurrent 27-day variation of solar wind parameters as well as that of GCR intensities are ~50% larger for positive (A>0) polarity epochs of solar magnetic cycles, than for the A0 than for the A0 than when A0 periods than in the negative A<0 periods.
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