Earth's Magnetic Weak Spot Expands: ESA's Swarm Satellites Reveal Rapid Growth of the South Atlantic Anomaly
Scientists Uncover Widening Weak Zone in Earth's Magnetic Field
Using 11 years of magnetic filed data from the European Space Agency's Swarm satellites, scientists have found that the South Atlantic Anomaly—a weak spot in Earth's magnetic field—has grown by nearly half the size of continental Europe since 2014.
Earth's magnetic field is essential for sustaining life, shielding the planet from harmful cosmic rays and solar particles. Generated by a vast ocean of molten iron swirling about 3,000 kilometers below the surface, this dynamic force behaves like a colossal dynamo, producing electrical currents that create and continuously alter our magnetic field—though the true mechanisms are far more intricate.
Swarm, an Earth Explorer mission under ESA's Earth Observation FutureEO programme, consists of three identical satellites designed to measure magnetic signals originating from Earth's core, mantle, crust, oceans, ionosphere and magnetosphere. This groundbreaking mission offers scientists unprecedented insight into the planet's magnetic sources, helping them uncover why certain regions are weakening while others strengthen. The South Atlantic Anomaly, a particularly weak magnetic areas, was first detected southeast of South America in the 19th century.
Growing Concern Among Space Scientists
Today, the South Atlantic Anomaly attracts growing concern the space industry, as satellites crossing this weakened magnetic zone are exposed to elevated levels of cosmic radiation. Such exposure can cause hardware malfunctions, system failures, and even complete communication blackouts.
A new study published in Physics of the Earth and Planetary Interiors reveals that the South Atlantic Anomaly has steadily expanded between 2014 and 2025. However, researchers found an area of the Atlantic Ocean southwest of Africa where Earth's magnetic field has weakened even more rapidly since 2020.
Lead author Professor Chris Finlay of the Technical University of Denmark explained, "The South Atlantic Anomaly is not uniform—it's evolving differently near Africa compared to South America. Something distinctive in this region is driving a more pronounced weakening."
What Lies Beneath: Reverse Flux Patches and the Molten Core
The phenomenon is linked to unusual magnetic field patterns at the boundary between Earth's molten outer core and solid mantle, known as reverse flux patches.
Professor Chris Finlay explained, "Ordinarily, magnetic field lines in the southern hemisphere emerge from Earth's core. However, beneath the South Atlantic Anomaly, we're observing something unexpected—regions where the field lines, instead of rising outward, dive back into the core. Swarm's precise data reveal one such region drifting westward beneath Africa, further contributing to the anomaly's weakening."
Swarm's Record-Breaking 11 Years of Magnetic Mapping
A Landmark Mission for Earth Observation
The latest model of Earth's core-driven magnetic field represents a major milestone for ESA's Swarm mission, now boasting the longest continuous record of magnetic field measurements ever gathered from space.
Launched on 22 November 2013 as ESA's fourth Earth Explorer mission, the Swarm satellites were designed as pathfinders under the FutureEO programme. Initially conceived as technology demonstrators, they have far exceeded expectations—outlasting their design lifespan, becoming vital to long-term scientific records, supporting key operational services and paving the way for future Earth-observing missions.
Swarm data now form the backbone of global magnetic models essential for navigation, monitoring space weather and revealing new insights into the Earth system, from its deep core to the outermost atmosphere.
Earth's Magnetic Field Strengthens Over Siberia
Dynamic Shifts in Earth's Magnetic Poles
The latest findings from ESA's Swarm mission underscore the ever-changing nature of Earth's magnetic field. In the southern hemisphere, there exists a single point of exceptional magnetic strength, while in the north, two such regions are found—one over Canada and the other across Siberia.
"When studying Earth's magnetism, it's crucial to recognize that it isn't simple dipole like a bar magnet," explained Professor Chris Finlay. "Only through satellites such as Swarm can we accurately map this intricate structure and observe its continual evolution."
Since the launch of ESA's Swarm mission, Earth's magnetic field has shown contrasting trends—strengthening over Siberia while weakening above Canada. The Canadian magnetic region has shrunk by 0.65% of the planet's surface, roughly equivalent ot India's size, whereas the Siberian field has expanded by 0.42%, an area similar to Greenland.
Magnetic Drift and Global Implications
The shift, driven by turbulent motions within Earth's molten core, has caused the north magnetic pole to drift towards Siberia—a movement with significant implications for global navigation systems.
"It's marvellous to see the broader picture of our dynamic planet through Swarm's long-term observations," said ESA's Mission Manager, Anja Strømme. "All three satellites remian in excellent condition and we expect to continue gathering valuable data well beyond 2030, particularly during the next solar minimum."
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