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

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 Sunʹs magnetic polarity cycles, qA > 0 and qA < 0, were observed in the time profile of the 27-day variation of galactic cosmic rays. The amplitude of the calculated 27-day variation of galactic cosmic rays is not depend on the tilt angles of the heliospheric neutral sheet for both qA > 0 and qA < 0 cycles. The expected amplitude (from theoretical modeling of galactic cosmic rays transport) of the 27-day variation is greater in the 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.