The modulation of galactic cosmic rays (GCRs) by solar activity is a fundamental aspect of heliospheric physics. In this study, we investigate the relationship between annual mean cosmic ray intensity variations recorded by the Thule Neutron Monitor and the occurrence of halo coronal mass ejections (CMEs), including X-class and M-class flare–associated halo CMEs, during Solar Cycles 23 and 24. Correlation analysis was performed using annual mean data to quantify the degree of association between cosmic ray intensity variations and solar eruptive phenomena.
The results reveal a significant inverse relationship between cosmic ray intensity and halo CME activity in both solar cycles. During Solar Cycle 23, a strong negative correlation (r = −0.71) was found between cosmic ray intensity variations and total halo CME occurrence. The relationship was moderately negative for X-class flare–associated halo CMEs (r = −0.46) and strongly negative for M-class flare–associated halo CMEs (r = −0.86), indicating a pronounced influence of these events on cosmic ray modulation. During Solar Cycle 24, moderate negative correlations were observed between cosmic ray intensity variations and total halo CMEs (r = −0.51), X-class flare–associated halo CMEs (r = −0.44), and M-class flare–associated halo CMEs (r = −0.45).
The consistently negative correlations demonstrate that increased solar eruptive activity is associated with reduced cosmic ray intensity near Earth, supporting the established concept of solar modulation of galactic cosmic rays. Furthermore, the stronger correlations observed during Solar Cycle 23 compared with Solar Cycle 24 suggest that the more intense solar and heliospheric conditions of Cycle 23 exerted a greater influence on cosmic ray transport and suppression. These findings contribute to a better understanding of the interplay between solar transients and cosmic ray variability and highlight the importance of halo CMEs as indicators of heliospheric disturbances affecting the near-Earth space environment.
KEYWORDS
Cosmic Ray Intensity Variations, Thule Neutron Monitor, Halo Coronal Mass Ejections (CMEs), X-Class Solar Flares, Galactic Cosmic Rays, Solar Modulation.
Ajay Kumar Saket1*, Nand Kumar Patel2
1Research Scholar PM Excellence, Chhatrasal Govt. P. G. College, Panna- 488001, M.P., India
2Department of Physics PM Excellence, Chhatrasal Govt. P. G. College, Panna- 488001, M.P., India