Proc. IAU volume 13, issue S335, P197-200 2017 DOI: 10.1017/s1743921317010146 View full text
Kalevi Mursula, Lauri Holappa

Abstract: We use the principal component analysis (PCA) to study geomagnetic activity at annual resolution using a network of 26 magnetic stations in 1966-2015, and an extended network of 40 stations in 1980-2015. The first principal component (PC1) describes the long-term evolution of global geomagnetic activity, and has an excellent correlation with indices like the Kp/Ap index. The two networks give identical results for PC1. The second principal component (PC2) is highly correlated with the annual percentage of hig…

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