Analysis of Galactic Cosmic Ray Anisotropy During the Time Period from 1996 to 2020

Abstract

We study the influence of drift effects on the galactic cosmic ray anisotropy (GCRA) in different periods of solar activity (from 1996 to 2020) using data from the global network of neutron monitors. We analyze the GCRA in 1996, the last year of Solar Cycle 22 with positive polarity (A>0), Solar Cycles 23 and 24 with both positive (A>0) and negative polarities (A<0), and the 2020 onset of Solar Cycle 25 with positive polarity (A>0). We show that in positive polarity periods, a diffusion model with noticeably manifested drift is acceptable, whereas the diffusion-dominated model of galactic cosmic ray (GCR) transport is more acceptable in negative polarity periods.We found that the average radial component of the drift vector for A>0 practically points to 12 h, and for the A<0 polarity to 24 h, respectively. These results are consistent with the drift theory of modulation of GCRs. According to theory, during positive or negative polarity periods, a drift stream of GCRs is directed away from or toward the Sun, respectively, thus giving rise to long-term changes of the radial component of the GCRA.The calculated magnitudes of the radial and tangential components of the GCRA in different sectors of the heliospheric magnetic field were used to calculate the parameters that characterize the GCR modulation in interplanetary space.