  In this paper, we study two sets of local geomagnetic indices from 26
stations using the principal component (PC) and the independent component (IC)
analysis methods. We demonstrate that the annually averaged indices can be
accurately represented as linear combinations of two first components with
weights systematically depending on latitude. We show that the annual
contributions of coronal mass ejections (CMEs) and high speed streams (HSSs) to
geomagnetic activity are highly correlated with the first and second IC. The
first and second ICs are also found to be very highly correlated with the
strength of the interplanetary magnetic field (IMF) and the solar wind speed,
respectively, because solar wind speed is the most important parameter driving
geomagnetic activity during HSSs while IMF strength dominates during CMEs.
These results help in better understanding the long-term driving of geomagnetic
activity and in gaining information about the long-term evolution of solar wind
parameters and the different solar wind structures.
