THE CHARACTERISTICS OF GREAT COSMIC RAY STORM EVENTS IN MARCH 1989

The characteristics of Forbush decreases of cosmic ray caused by solar flares in March 1989 are analysed in this paper. The anisotropy for μ-meson component are also analysed beside neutron component, and the relationship between the cosmic ray intensity variation and the characteristics of solar flares and geomagnetic activities are discussed. The results show-that Forbush decreases not only bear a relation to the importances, duration and angular distance from the central meridiam of solar flares, but also depend on whether the optical flares are accompanied by strong X-ray bursts and radio bursts, as well as followed by geomagnetic storms of sudden commencement type. The anisotropic analysis shows that the anisotropy of the large cosmic ray storm events in March was obviously weaker than that of the cosmic ray intensity during the quiet days. It is probably because that strong solar activity could reduce the degree of the cosmic ray anisotropy.