THE RELATIONSHIP BETWEEN FORBUSH DECREASE, GEOMAGNETIC STORMS AND CORONAL MASS EJECTIONS

We conducted a comprehensive investigation into the relationship between Forbush decreases (FDs), Geomagnetic storms (GS), and Coronal mass ejections (CMEs) during Solar cycles (SC) 23 and 24. GS characterized by the Dst index, do not consistently occur alongside FDs, and conversely. FDs are not always accompanied by GS. Our study analyzed the interdependencies among interplanetary parameters, including FDs, the Dst index, solar wind speed, and the Interplanetary magnetic field (IMF). FDs associated with halo CMEs exhibited a significantly higher correlation compared to those linked with non-halo CME events. Furthermore, halo CMEs play a critical role in triggering larger-amplitude FDs and intense geomagnetic storms, whereas non-halo CMEs tend to result in smaller FD amplitudes. We found that 28.3% were associated with halo CMEs, while the remaining 71.7% were linked to non-halo CMEs. The results indicate that the distribution of FDs and geomagnetic storms varies markedly between the maximum and minimum phases of solar activity.