Research Article

Sensitivity of the auroral zones to temporal changes in Earth’s internal magnetic field

¹ Institute of Geophysics, ETH Zurich, Sonneggstrasse 5, 8092 Zürich, Switzerland
² School of Earth and Environment, University of Leeds, Leeds, LS2 9JT, UK

^* Corresponding author: stefano.maffei@eaps.ethz.ch

Received: 16 December 2024
Accepted: 17 April 2025

Abstract

It is commonly accepted that the shape and temporal evolution of the auroral zones (here defined as the climatological average of the auroral ovals) are primarily influenced by the dipolar and high-latitude features of the geomagnetic field. Though recent studies challenge this view, a systematic approach to linking the joint evolution of auroral zones and geomagnetic fields are currently missing. Here we attempt to fill this gap via the introduction of a novel technique, based on a Green’s function approach, that allows exploration of the sensitivity of the auroral zones to regional changes of the internally generated magnetic field at the core-mantle-boundary (CMB). We define key diagnostics for the auroral zones’ shapes and location: the auroral zone surface area, the location of their centroid (i.e., their geometric centre), and the distance between the zones and selected cities. We focus on the temporal period covered by ESA’s Swarm mission. We find that temporal changes in the dipolar field dominate the variation in the location of the auroral zones, i.e., their centroid latitudes and distances from selected locations. However, non-dipolar contributions play and important role, especially in the Northern Hemisphere. In particular, they dominate changes in the northern auroral zone surface area and offset the dipolar contribution to the distance from Northern England locations. Furthermore, we show that all diagnostics are influenced by geomagnetic field changes that are globally distributed on the surface of the Earth’s core, and not only in the polar regions. We found significant contribution, from the mid-to-low latitude regions and, in particular, from the same geomagnetic features responsible for the existence of the South Atlantic Anomaly. Our methodology thus provides a link between polar and mid-to-low latitude features of interest for space weather and space climate.