Long-term satellite observations reveal that Earth’s magnetic field is changing more rapidly and unevenly than scientists once expected, reflecting complex and dynamic processes deep within the planet’s interior. Using more than a decade of high-precision measurements from the European Space Agency’s Swarm satellite constellation, researchers have gained unprecedented insight into how magnetic forces generated thousands of kilometres below the surface are evolving over time, with important implications for life on Earth, space safety, and navigation.
One of the most striking findings concerns the South Atlantic Anomaly, a vast region of unusually weak magnetism stretching over parts of South America and the southern Atlantic Ocean. Since 2014, this weak zone has expanded steadily, growing by an area nearly half the size of continental Europe. Earth’s magnetic field in this region has not only weakened but has done so unevenly, with particularly rapid declines observed since 2020 in areas southwest of Africa. This behaviour highlights that the anomaly is not a single, uniform feature, but a complex structure changing differently across regions.
The magnetic field is vital to sustaining life, as it shields the planet from harmful cosmic radiation and charged particles emitted by the Sun. Generated by the motion of molten iron in Earth’s outer core, roughly 3,000 kilometres beneath the surface, the field arises from electrical currents produced by turbulent flows of liquid metal. Swarm’s unique configuration of three identical satellites allows scientists to disentangle magnetic signals originating from the core, mantle, crust, oceans, ionosphere, and magnetosphere, providing a far clearer picture of the processes shaping Earth’s magnetic field.
Researchers have linked the unusual behaviour of the South Atlantic Anomaly to features known as reverse flux patches at the boundary between the liquid outer core and the solid mantle. In these areas, magnetic field lines behave in unexpected ways, looping back into the core instead of emerging outward. Swarm data show that at least one such patch is drifting westward beneath Africa, intensifying the weakening of the magnetic field in that region and contributing to the anomaly’s growth.
Beyond the South Atlantic, Swarm observations also reveal significant changes elsewhere on the planet. While the magnetic field has weakened over Canada, it has strengthened over Siberia, causing shifts in the size and position of regions where magnetism is particularly intense. These changes are linked to the recent movement of the northern magnetic pole toward Siberia, a development that directly affects navigation systems reliant on accurate magnetic models. Such findings underscore that Earth’s magnetic field is far from a simple, static dipole, but a constantly evolving system shaped by deep Earth dynamics.
With more than 11 years of continuous measurements, the Swarm mission now provides the longest space-based record of magnetic field data. This extended time series underpins global navigation models, supports space weather monitoring, and offers new insights into Earth’s structure from its core to the edge of its atmosphere. As the satellites remain healthy, scientists hope to extend observations beyond 2030, allowing even deeper understanding of the forces driving Earth’s magnetic field and its ongoing transformation.