27-day Variations of the Galactic Cosmic Ray Intensity and Anisotropy∗

We study the relationships of the 27-day variations of the galactic cosmic ray (GCR) intensity and anisotropy with the 27-day variations of the solar wind (SW) velocity, Wolf number (Rz) and interplanetary magnetic field (IMF) strength for different positive (A > 0) and negative (A < 0) polarity periods of the solar magnetic cycles based on the experimental data. We found that the long-lived active region of the longitudes (with life time more than 22 years) exists on the Sun. This phenomenon is clearly manifested for the A > 0 period of the solar magnetic cycle. The stable long-lived active region of the longitudes on the Sun is the source of the 27-day variation of the SW velocity. The maximum of the phase distribution of the 27-day variation of the SW velocity versus the heliolongitudes is preceded by 170◦–180◦ the maxima of the phases distributions of the 27-day variations of the GCR intensity and anisotropy for the A > 0 polarity period. When comparing the theoretical calculations (obtained by the numerical solutions of the Parker’s transport equation) with the experimental data we conclude that the 27-day variation of the solar wind velocity is the general source of the 27-day variations of the GCR intensity and anisotropy. The average amplitudes of the 27-day variations of the galactic cosmic ray anisotropy and intensity for the minima epochs of solar activity are larger in the A > 0 period than in the A < 0 period at the Earth orbit.