Abstract
We study the 27-day variations of the galac- tic cosmic ray (GCR) intensity and three dimensional (3-D) anisotropy in different polarity periods of the solar magnetic cycle. We found that the larger amplitudes of the 27-day vari- ations of the galactic cosmic ray anisotropy and intensity in the minimum epochs of solar activity for the A> 0 polarity period than for the A 0 polarity period. The 27-day variation of the GCR 3-D anisotropy has a sporadic character; it appears and disappears as wave packages (wave oscillations) with an average duration of 4-6 solar rotations. We found that the rigidity R power law spectrum of the am- plitudes (A27) of the 27-day variation of the GCR intensity (A27/R ) is hard ( = 0.54± 0.11) in the A> 0 polar- ity period (1996-1997) and is soft ( = 0.95± 0.12) in the A< 0 period (1986-1987).
Highlights
To study the 27-day variations of the galactic cosmic ray (GCR) intensity and anisotropy the minimum epoch of solar activity is very useful
The directions of the solar wind velocity and drift velocity of the GCR protons coincide for the A > 0 polarity period in contrary to the A < 0 period
Using the frequency filters method (Otnes and Enochson, 1972) we demonstrate some features of the 27-day variation of the GCR anisotropy for the sequence of the individual Carrington rotations in the A > 0 and A < 0 polarity periods
Summary
To study the 27-day variations of the GCR intensity and anisotropy the minimum epoch of solar activity is very useful. Throughout the minimum epochs of solar activity the disturbances in the interplanetary space are minimal and a polarity of the Sun’s global magnetic field is well established. For this epoch the contribution of the drift effect of the GCR particles (due to gradient and curvature of the regular interplanetary magnetic field) can be revealed reasonably clearly in different classes of GCR variations; that is especially vital for the GCR variations with relatively small amplitudes, e.g
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