A new method to estimate annual solar wind parameters and contributions of different solar wind structures to geomagnetic activity

TL;DR

This study uses principal and independent component analysis on geomagnetic indices to quantify how different solar wind structures, like CMEs and HSSs, influence geomagnetic activity and their relation to solar wind parameters.

Contribution

It introduces a novel application of PC and IC analysis to separate and quantify the contributions of solar wind structures to geomagnetic activity over long periods.

Findings

Annual geomagnetic indices are linear combinations of two main components.

Coronal mass ejections correlate with the first independent component.

High speed streams correlate with the second independent component.

Abstract

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.