Quantitative Assessment of Cosmic Ray Modulation Associated with Coronal Mass Ejections During Solar Cycles 23–25

सार

Galactic cosmic ray (GCR) intensity near Earth exhibits pronounced variability due to long-term solar cycle modulation as well as short-term transient disturbances associated with solar activity. Among these transient drivers, coronal mass ejections (CMEs) play a particularly important role by modifying heliospheric magnetic field conditions and solar wind properties, thereby influencing the transport of high-energy charged particles through the heliosphere.

In this study, a quantitative assessment of cosmic ray modulation associated with CMEs is carried out for Solar Cycles 23–25. Neutron monitor observations are used as a proxy for GCR intensity, while CME event information is obtained from established coronagraph-based catalogues. A physically motivated association criterion based on interplanetary propagation delay is applied to relate CME occurrences with observed transient cosmic ray decreases, including Forbush decrease events.

The analysis shows that CME-associated disturbances consistently produce stronger and more sustained suppressions of cosmic ray intensity compared to periods without significant CME activity. A cycle-wise comparison reveals clear differences in modulation behavior: Solar Cycle 23 exhibits frequent and deeper cosmic ray depressions corresponding to its higher level of solar activity, Solar Cycle 24 shows comparatively weaker modulation signatures, and Solar Cycle 25 indicates a gradual enhancement of CME-related effects during its rising phase. These results confirm the central role of CMEs in short-term cosmic ray modulation and highlight the importance of background heliospheric conditions in shaping cycle-dependent responses. The study provides observational insights relevant to heliospheric physics and space weather research.