Abstract
Monthly coronal mass ejection (CME) counts, - for all CMEs and CMEs with widths > 30 ◦ , - and monthly averaged speeds for the events in these two groups were com- pared with both the monthly averaged cosmic ray intensity and the monthly sunspot number. The monthly Pi-index, which is a linear combination of monthly CME count rate and aver- age speed, was also compared with the cosmic ray intensity and sunspot number. The main finding is that narrow CMEs, which were numerous during 2007 - 2009, are ineffective for modulation. A cross-correlation analysis, calculating both the Pearson (r) product-moment correlation coefficient and the Spearman (ρ) rank correlation coefficient, has been used. Be- tween all CMEs and cosmic ray intensity we found correlation coefficients r =− 0.49 and ρ =− 0.46, while between CMEs with widths > 30 ◦ and cosmic ray intensity we found r =− 0.75 and ρ =− 0.77, which implies a significant increase. Finally, the best expres- sion for the Pi-index for the examined period was analyzed. The highly anticorrelated be- havior among this CME index, the cosmic ray intensity (r =− 0.84 and ρ =− 0.83), and the sunspot number (r =+ 0.82 and ρ =+ 0.89) suggests that the first one is a very useful solar-heliospheric parameter for heliospheric and space weather models in general.
Published Version
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