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Principal Component Analysis of Geomagnetic Activity: New Information on Solar Wind

  • Kalevi Mursula (a1) and Lauri Holappa (a1)

We use the principal component analysis 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 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 the first principal component. The second principal component is highly correlated with the annual percentage of high-speed streams (HSS). The extended network has a slightly higher sensitivity to HSSs. We verify the non-trivial latitudinal distribution of the second empirical orthogonal function. We find that the amplitude of the 22-year variation of geomagnetic activity has a closely similar latitudinal distribution as the second empirical orthogonal function. This verifies that the 22-year variation of geomagnetic activity is related to HSSs. The most likely cause is the Russell-McPherron mechanism.

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Cliver, E. W., Boriakoff, V. & Boumar, K. H. 1996, J. Geophys. Res., 101, 27, 091
Holappa, L., Mursula, K., Asikainen, T. & Richardson, I. G., 2014, J. Geophys. Res., 119, 4544
Mursula, K. & Martini, D., 2007, Geophys. Res. Lett., 34, L22, 107
Russell, C. T. & McPherron, R. L., 1973, J. Geophys. Res., 78, 92
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Proceedings of the International Astronomical Union
  • ISSN: 1743-9213
  • EISSN: 1743-9221
  • URL: /core/journals/proceedings-of-the-international-astronomical-union
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