Long-term variations of geomagnetic activity and their solar sources

TL;DR

This paper investigates the long-term patterns of geomagnetic activity throughout solar cycles, identifying components related to the Sun's magnetic properties and solar wind sources, and how these influence geomagnetic variations.

Contribution

It reveals how the geomagnetic activity floor depends on the Sun's magnetic moment and how it can indicate the amplitude of the sunspot cycle.

Findings

Geomagnetic activity floor depends on the Sun's magnetic moment.

The activity floor can predict sunspot cycle amplitude.

Different parts of geomagnetic activity relate to specific solar phenomena.

Abstract

Geomagnetic activity in each phase of the solar cycle consists of 3 parts: (1) a floor below which the geomagnetic activity cannot fall even in the absence of sunspots, related to moderate graduate commencement storms; (2) sunspot-related activity due to sudden commencement storms caused by coronal mass ejections; (3) graduate commencement storms due to high speed solar wind from solar coronal holes. We find that the changes in the floor depend on the global magnetic moment of the Sun, and on the other side, from the height of the floor we can judge about the amplitude of the sunspot cycle.