Researchers analysing 11 years of measurements from ESA’s Swarm satellites report that the South Atlantic Anomaly — a weakened patch in Earth’s magnetic field — has expanded significantly since about 2014, by an area roughly half the size of continental Europe. The weakening appears linked to unusual structures at the boundary between the liquid outer core and the solid mantle, with an anomalous zone moving westward over Africa. Concurrent changes include a stronger field over Siberia and a weaker field over Canada. Scientists warn the evolving anomaly can increase radiation exposure and the risk of malfunctions for satellites and crewed missions in low Earth orbit.
Growing South Atlantic Anomaly Could Put Satellites at Risk, New Study Warns
Researchers analysing 11 years of measurements from ESA’s Swarm satellites report that the South Atlantic Anomaly — a weakened patch in Earth’s magnetic field — has expanded significantly since about 2014, by an area roughly half the size of continental Europe. The weakening appears linked to unusual structures at the boundary between the liquid outer core and the solid mantle, with an anomalous zone moving westward over Africa. Concurrent changes include a stronger field over Siberia and a weaker field over Canada. Scientists warn the evolving anomaly can increase radiation exposure and the risk of malfunctions for satellites and crewed missions in low Earth orbit.
03:52 PM, 11/11/2025Science
Growing weak spot in Earth's magnetic shield raises concerns for satellites
Scientists tracking changes in Earth's magnetic field have identified a widening weakened region above the South Atlantic — the South Atlantic Anomaly (SAA) — that may increase radiation exposure for spacecraft and satellites in low Earth orbit.
The planet's magnetic field, which protects life by deflecting cosmic radiation and energetic particles from the Sun, is generated by convective flows of molten iron in Earth’s outer core roughly 3,000 km below the surface. Those flows produce electrical currents that give rise to the global magnetic envelope, but the detailed processes that drive and alter the field remain complex and under active study.
Using 11 years of measurements from ESA’s three-satellite Swarm constellation (launched in 2013), researchers analysed magnetic signals from the core, mantle, crust, oceans and upper atmosphere. Their study, published in Physics of the Earth and Planetary Interiors, reports that the SAA has expanded since about 2014 by an area roughly half the size of continental Europe.
"The South Atlantic Anomaly is not just a single block. It’s changing differently towards Africa than it is near South America. There’s something special happening in this region that is causing the field to weaken in a more intense way," — Chris Finlay, lead author, Technical University of Denmark.
Researchers link the distortion to unusual structures at the boundary between the liquid outer core and the overlying solid mantle. Instead of the magnetic field lines emerging smoothly from the core in the southern hemisphere, the team observed zones where field lines are directed back into the core. Swarm data show one such anomalous zone moving westward over Africa, which helps explain why the SAA is weakening more rapidly in that sector.
The study also notes concurrent changes in the northern hemisphere: a strengthening of the field over Siberia and weakening over Canada. Those shifts affect the balance between northern high-field regions and influence satellite navigation and positioning systems that depend on local magnetic models.
Implications for satellites and crewed missions
For spacecraft flying through the SAA, the weakened magnetic shielding permits higher fluxes of energetic particles to reach instruments and electronics. That can increase the risk of single-event upsets, damage to hardware, temporary malfunctions or outages, and higher cumulative radiation doses for satellites and crewed missions such as the International Space Station.
Operators can mitigate some risks by adjusting satellite operations, improving radiation hardening, or updating orbit and exposure forecasts — but the evolving anomaly underscores the importance of continuous monitoring and improved models of Earth’s core and magnetic field.
What’s next?
Scientists will continue to use Swarm and other observations to track the SAA and refine models that link core dynamics to surface magnetic changes. Understanding these processes better will help predict future evolution of the anomaly and guide steps to protect satellites and human activities in low Earth orbit.