Scientists Find Expanding Weakness in Earth's Magnetic Shield

A significant area of weakness in the Earth’s protective magnetic field has enlarged and altered its form since 2014. (Image credit: ESA (Data source: Finlay, C.C. et al., 2025))

A zone of reduced magnetic intensity above the South Atlantic has expanded substantially since 2014, according to findings from satellite measurements.

The region, referred to as the South Atlantic Anomaly, has increased by nearly half the landmass of the European continent, extending a section toward the African continent, where the magnetic protection is diminishing at the highest rate.

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“The South Atlantic Anomaly isn’t simply a uniform entity,” stated Chris Finlay, the study’s primary author and a geomagnetism professor at the Technical University of Denmark. “Its rate of change differs in the direction of Africa versus South America. Unique events occurring in this area are producing a more intense field weakening effect.”

Researchers initially noted the South Atlantic Anomaly in the nineteenth century. Within the anomaly’s boundaries, the magnetic intensity emanating from Earth’s core decreases to a level around 120 miles (200 kilometers) above the terrestrial surface, a considerable deviation from the normal 400 miles (650 km) field altitude.

This creates potential risks for orbiting satellites and other space vehicles. The magnetic field around the Earth serves to defend our planet and its orbiters from irradiated particles stemming from the sun, alongside X-ray and UV radiation; consequently, space vehicles traveling across the South Atlantic Anomaly are subjected to stronger radiation levels, potentially leading to operational failures, physical damage, and even electrical disruptions, according to available information.

Finlay and his fellow researchers suggest that unusual fluxes located at the boundary layer separating Earth’s mantle and outer core, found within Earth’s internal structure between the outer crust and the inner core, are responsible for both the anomaly’s expansion and eastward progression.

A substantial portion of Earth’s magnetic field comes from our planet’s external liquid core.

The Earth’s external core, a massive region consisting of spiraling, molten iron approximately 1,900 miles (3,000 km) below the Earth’s surface, largely contributes to the formation of Earth’s magnetic field. The electrical current originating from liquid iron movement generates a magnetic field, extending upwards into the mantle and further into Earth’s atmospheric layers, and manifesting as two expansive ring structures converging at the poles.

Earlier scientific discoveries have revealed instances where magnetic force created by the outer core curves back inwards instead of projecting outwards around the South Atlantic Anomaly. These reverse flux patches are subject to movement and growth, which Finlay believes accounts for the South Atlantic Anomaly’s growth over the past decade.

“We have observed one such zone drifting westward in the direction of Africa, contributing to the diminishing magnetic field [strength] of the South Atlantic Anomaly in that locale,” he stated.

Over the last ten years, regions with noticeably enhanced magnetic intensity located in both Canada and Siberia have displayed variations.

The team discovered these irregular shifts by analyzing data from the European Space Agency’s (ESA) continuing Swarm project, utilizing a trio of identical satellites monitoring magnetic activity emerging from Earth’s interior and the oceans. These readings also highlighted alterations within magnetic patterns impacting Canada and Siberia, with levels appearing more intense compared to those measured since the commencement of the Swarm mission back in 2013.

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According to research findings, the strength of the magnetic field above Canada has slightly decreased from 2014 onwards, while conversely, the field above Siberia has become more intense. The robust magnetic zone spanning Canada has diminished by nearly the size of India, whereas the Siberian zone has grown to encompass an area similar to Greenland. Researchers attribute these modifications to recent shifts in the Earth’s northern magnetic pole drifting towards Siberia; however, longer-term surveillance remains essential to monitor subsequent dynamic changes.

“It’s incredibly enriching to visualize the complex interactions of our dynamic Earth,” conveyed Anja Strømme, the Swarm mission manager for ESA, within the press statement. “With our satellites operating optimally and supplying us with excellent data, we have confidence we can prolong observations beyond 2030.”

TOPICSEarth’s InteriorEuropean Space Agency

Sascha PareSocial Links NavigationStaff writer

Sascha is a staff writer for Live Science, working from the U.K. She graduated from the University of Southampton in England with a bachelor’s degree in biology and from Imperial College London with a master’s degree in science communication. Her previous publications include pieces for The Guardian and the health website Zoe. Away from her desk, she can be found playing tennis, baking bread, and searching for hidden treasures in vintage shops.

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