CORRELATIVE STUDY OF SOLAR-ACTIVITY AND COSMIC-RAY INTENSITY

We perform a correlative study of solar activity (sunspot numbers) and cosmic ray intensity (neutron monitor count rates) for the last four solar cycles. Analysis of the running cross correlation between the tw o series shows that the behavior of cosmic ray modulation is similar, in general, for particles with different energy. However, a strong rig idity dependence as well as an unusual behavior of the cross correlati on function is found for the descending phase of cycle 20. We study th e evolution of cosmic ray and solar activity cycles in a three-dimensi onal phase space by means of the delayed component method. While all s olar activity cycles and most cosmic ray cycles are planar, cosmic ray cycle 20 is significantly three-dimensional. A concept of the momenta ry phase of a cycle is introduced, and the phase evolution of cosmic r ay and solar activity cycles is studied. We also discuss the heliosphe ric conditions responsible for the unusual behavior of cosmic ray modu lation in the descending phase of cycle 20.