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

Neutron monitor, solar and geomagnetic activity data have, been used to investigate variations of galactic cosmic ray intensity connected with the Sun's 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 solar magnetic cycles. At the same time, during the minima and near minima epochs of solar activity the average amplitudes of the 27-day variations of galactic cosmic rays for neutron monitors are about 1.5 times greater for the qA >0 cycle than for the qA <0 cycle. (C) 2001 COSPAR. Published by Elsevier Science Ltd. All rights reserved.