The Earth’s magnetic field, often likened to an invisible shield, has long been credited with protecting our planet from the relentless bombardment of cosmic and solar radiation. But this protective barrier is not without its vulnerabilities. Recent research, published October 14, 2025, in Physics of the Earth and Planetary Interiors, has revealed that a giant weak spot known as the South Atlantic Anomaly (SAA) has grown dramatically in both size and intensity over the past eleven years, raising questions and concerns among scientists and satellite operators alike.
The South Atlantic Anomaly stretches across the vast gulf that separates Africa from South America, encompassing much of the South Atlantic Ocean. According to Discover Magazine, the SAA has been a subject of scientific scrutiny since the 19th century, but only in the last decade—thanks to the European Space Agency’s Swarm mission—have researchers been able to monitor its changes in continuous detail. The Swarm mission, launched in 2013, consists of three satellites—Alpha, Bravo, and Charlie—tasked with mapping the intricacies of Earth’s magnetic field.
Swarm’s eleven years of data paint a striking picture. Since 2014, the SAA has expanded by an area nearly half the size of continental Europe. If one defines the anomaly as regions where the magnetic field strength falls below 26,000 nanoteslas (nT), the SAA now covers almost 1% more of Earth’s surface than it did just over a decade ago—an area roughly half as large as the United States, according to IFLScience. The weakest recorded region within the SAA has dropped from 22,430 nT in 2014 to 22,094 nT in 2025, illustrating a steady and measurable decline in magnetic intensity.
This isn’t just an academic curiosity. The SAA’s existence and growth have real-world consequences, especially for satellites and astronauts operating in low-Earth orbit. As ScienceAlert notes, the SAA is the primary region where satellites are exposed to elevated doses of cosmic radiation. This can lead to immediate electronic malfunctions and, over time, structural damage to sensitive equipment. The anomaly’s location—where the inner Van Allen radiation belt dips closest to Earth—means satellites passing overhead are particularly vulnerable.
What’s behind this growing dent in our planet’s shield? The SAA’s formation and evolution are tied to the complex, churning motions of molten iron within Earth’s outer core. This dynamic flow generates the magnetic field, but it’s not a simple, static process. “The South Atlantic Anomaly is not just a single block,” explained Professor Chris Finlay, a geomagnetism expert at the Technical University of Denmark and lead author of the new study. “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.”
One of the most intriguing findings from Swarm’s data is the presence of so-called reverse flux patches—areas where magnetic field lines, which normally emerge from Earth’s core in the southern hemisphere, instead plunge back into the core. “Normally we’d expect to see magnetic field lines coming out of the core in the southern hemisphere,” Finlay elaborated. “But beneath the South Atlantic Anomaly we see unexpected areas where the magnetic field, instead of coming out of the core, goes back into the core. Thanks to the Swarm data we can see one of these areas moving westward over Africa, which contributes to the weakening of the South Atlantic Anomaly in this region.”
This reversed magnetic flux may be linked to a mysterious geological feature known as the African Large Low-Shear-Velocity Province (LLSVP), a massive, super-hot blob of material at the boundary between Earth’s core and mantle. Scientists suspect that the LLSVP could disrupt the convection patterns in the core, further complicating the behavior of the magnetic field above it. While the exact relationship between the SAA and the LLSVP remains uncertain, the connection underscores just how much remains to be learned about the deep workings of our planet.
The SAA isn’t the only region where Earth’s magnetic field is in flux. The Swarm study also documented notable changes in the northern hemisphere. Over Siberia, a strong magnetic field region has grown by 0.42% of Earth’s surface area—about the size of Greenland—while the strong field region over Canada has shrunk by 0.65% of the planet’s surface, roughly the size of India. The strengthening over Siberia is associated with the northern magnetic pole’s ongoing drift toward that region, a trend that could have significant implications for navigation systems worldwide.
Despite the SAA’s dramatic growth and the attention it garners, scientists caution against alarmism. According to IFLScience, the SAA poses little threat to life on the ground; Earth’s atmosphere continues to provide robust protection against radiation. However, the situation is different for satellites and astronauts. The increased exposure to radiation can trigger both immediate failures and contribute to long-term cumulative damage, prompting space agencies to carefully monitor and manage satellite trajectories.
It’s worth noting that the SAA’s expansion is not evidence of an imminent magnetic pole reversal—a phenomenon where Earth’s north and south magnetic poles swap places. While such reversals have occurred throughout geological history, the current changes observed in the SAA are localized and not indicative of a global shift. “When you’re trying to understand Earth’s magnetic field, it’s important to remember that it’s not just a simple dipole, like a bar magnet,” Finlay emphasized. “It’s only by having satellites like Swarm that we can fully map this structure and see it changing.”
The Swarm satellites themselves have become unlikely heroes in this unfolding scientific story. Despite frequent exposure to heightened radiation as they pass over the SAA, all three satellites remain healthy and operational. Anja Stromme, Swarm mission manager at ESA, expressed optimism about the mission’s future: “The satellites are all healthy and providing excellent data, so we can hopefully extend that record beyond 2030, when the solar minimum will allow more unprecedented insights into our planet.”
Understanding the SAA and the broader dynamics of Earth’s magnetic field is more than an academic pursuit. The field plays a crucial role in maintaining our atmosphere, shielding life from harmful radiation, and enabling modern navigation. As the SAA continues to evolve, ongoing observations from missions like Swarm will be vital for protecting satellites, supporting space exploration, and deepening our knowledge of the restless forces shaping our planet from within.
As researchers continue to unravel the mysteries beneath our feet, the ever-changing magnetic field serves as a reminder that Earth is far from static—its deep interior is alive with movement, and its invisible shields are constantly shifting in ways that can ripple out to touch every aspect of life above.
