Vol. 11, Issue 9, Part C (2025)

In present study cosmic ray intensity following by a slow recovery typically lasting for several days is identified as Forbush decrease (Fd) event. As a result the geomagnetic index (Dst) decreased up to 300 nT, indicating a large geomagnetic storm and the percentage Fd decrease has gone to 16% giving rise a cosmic ray storm. Both events coincided with interplanetary conditions. Therefore, a systematic study has been performed to investigate the variation of cosmic ray intensity along with the interplanetary and geomagnetic disturbances. Results indicate a strong relationship between geomagnetic activity and Forbush decrease on short-term basis. Two types of interplanetary transient disturbances, namely magnetic cloud events and bidirectional events are analyzed to study the short-term changes in the solar wind (SW) plasma components as well as in cosmic ray intensity. A long-term trend of cosmic ray strength has been observed, with a peak occurring once every eleven years. The strength of cosmic rays is inversely related to solar activity. From 24-25 solar cycles, many parametric relationships between the sun and geophysical variables were studied. Investigating the effects of several sunspot cycles on the terrestrial plasma environment via changes in the solar characteristics that matter most. Furthermore, it seeks to investigate the relationship between the sunspot maximum's impact on geomagnetic activity and its amplitude. There is a clear change in the geomagnetic activity index that lines up with the sunspot cycle, which occurs every eleven years. However, solar flare maximums do not correspond to the peak of geomagnetic activity as measured over 27 days. From 24-25 solar cycles, geomagnetic indices correlate with parameters V and B. Both Ap and Kp follow a similar pattern of variation throughout the solar cycle's peak.