Study of cosmic ray intensity variations in relation to solar activity for sunspot cycles 19 to 23

Abstract

Based on the monthly data of various solar activity (SA) parameters, e.g. sunspot numbers (SSN), solar flux (SF), grouped solar flares (GSF), solar flare index (SFI) and coronal index (CI), a correlative study between solar activity (SA) and cosmic ray intensity (CRI, monthly mean of neutron monitor count rates) has been performed by the “running cross-correlation method”. Overall behaviour of the running cross-correlation function between CRI and different SA parameters is almost similar, except during the maxima of solar cycles. Moreover, the time-lag analysis has been performed by the method of “minimizing correlation coefficient” and it is found that observed time-lag between CRI and various SA parameters is similar, except the coronal index (CI). The time-lag is found to be larger for odd solar cycles (19, 21 and 23) in comparison to even solar cycles (20 and 22), showing odd-even asymmetry of solar cycles. The correlation between CRI and different SA parameters considering time-lag factor during the whole period of investigation has been presented. The differences observed in the time-lag between CRI and different SA parameters, especially for CI, have also been discussed.