For more than a decade, scientists have been tracking a mysterious weak spot in Earth’s magnetic field that’s baffling geophysicists and worrying satellite engineers. Known as the South Atlantic Anomaly, this vast region of weakened magnetism stretches between South America and Africa — and it’s expanding faster than anyone predicted.
According to recent data from the European Space Agency’s Swarm satellite mission, the anomaly has grown by an area roughly half the size of continental Europe since 2014, while its overall field intensity continues to decline. The findings are published in Physics of the Earth and Planetary Interiors, confirming that Earth’s core dynamo — the swirling ocean of molten iron that powers the planet’s magnetic shield — is far from stable.
The Planet’s Protective Field Is Warping
Earth’s magnetic field acts like an invisible force field, shielding us from charged solar particles and cosmic radiation. Without it, satellite electronics could fry in orbit, planes flying at high altitudes would be exposed to higher radiation levels, and our power grids could become unstable during solar storms.
But over the South Atlantic Anomaly, that magnetic armor is thinning out. Researchers describe it as a “dent” in the planet’s protective layer where the field strength dips below 26,000 nanoteslas — roughly 30% weaker than the global average.
“This region is changing differently toward Africa than it is near South America,” said Chris Finlay, professor of geomagnetism at the Technical University of Denmark and lead author of the new ESA study. “There’s something special happening in this region that is causing the field to weaken in a more intense way.”
Satellites in the Danger Zone
The South Atlantic Anomaly is more than a scientific curiosity — it’s a genuine technological threat. Spacecraft and satellites passing through this region are bombarded by higher doses of radiation because Earth’s protective magnetic bubble dips closer to the surface there.
According to ESA’s Swarm mission data, this has led to numerous satellite malfunctions over the years. Charged particles can disrupt onboard electronics, cause data corruption, and even temporarily shut down satellite instruments. NASA has long tracked the anomaly because it also grazes the International Space Station’s orbit, where astronauts occasionally experience brief radiation spikes during solar activity events.
The Great Molten Engine Below
Earth’s magnetic field originates deep underground, in the churning molten iron of the outer core — a dynamic, 2,900-kilometer-deep region that acts as a geophysical dynamo. As molten metal moves and convects, it generates electrical currents that produce magnetic forces spiraling out from the planet’s core into space.
Normally, this magnetic system behaves like a dipole, with a north and south pole. But under the South Atlantic, something strange is happening. ESA’s data shows regions where field lines, instead of flowing outward, turn back into the core — a phenomenon known as “reverse flux patches.”
“Normally we’d expect to see magnetic field lines coming out of the core in the southern hemisphere,” Finlay explained. “But beneath the South Atlantic Anomaly, we see unexpected areas where the magnetic field instead goes back into the core. One of these areas is now moving westward over Africa.”
This magnetic reversal is likely tied to deeper structures inside the planet, including an enormous hot rock formation called the African Large Low-Shear-Velocity Province, or LLSVP. This vast blob sits at the boundary between Earth’s mantle and core, and scientists believe it’s disrupting the flow of molten iron that powers our magnetic field.
A Living, Breathing Field
The Swarm satellites — launched in 2013 and orbiting in precise formation — have provided the longest continuous record of Earth’s magnetic variations ever collected. What they’ve found goes beyond just one growing anomaly. Earth’s magnetic field is alive, shifting and warping over multiple continents.
While the magnetic field weakens dramatically across the South Atlantic, it has been strengthening in some other areas. For example, the field over Siberia has grown by an area the size of Greenland, while a once-strong region over Canada has shrunk by an area roughly the size of India.
These regional fluctuations are connected to the magnetic north pole’s ongoing drift from Canada toward Siberia — a slow-motion migration that has been accelerating since the 19th century and has already forced updates to navigation systems worldwide.
A Magnetic Past (and Future)
The South Atlantic Anomaly may seem alarming, but Earth’s magnetic field has always been dynamic. Geological evidence suggests that reversals — where Earth’s north and south magnetic poles swap places — have occurred hundreds of times over millions of years. The last major reversal took place about 780,000 years ago, and partial, temporary excursions have happened since then.
That said, scientists say the current anomaly doesn’t signal an imminent pole flip. “The South Atlantic Anomaly doesn’t mean the entire field is collapsing,” said Finlay. “It’s more a sign of local complexity in how Earth’s core is moving beneath that region.”
Still, the data show that changes deep within our planet can happen much faster than previously thought — even within decades.
What This Means for Modern Technology
For most people, the South Atlantic Anomaly is invisible and harmless. But for satellites, astronauts, and long-distance communications, it’s a big deal. As the weak spot continues to expand, spacecraft designers must harden electronics against radiation exposure and plan flight paths that avoid prolonged exposure in that zone.
Space agencies are also closely watching how this region evolves. ESA’s Swarm mission manager, Anja Stromme, said the satellites are “healthy and providing excellent data” and that researchers hope to extend their monitoring beyond 2030. “The solar minimum coming up will allow us to gain unprecedented insights into how the magnetic field behaves when the Sun is calmer,” she said.
NASA and other agencies, including private satellite operators, are already integrating anomaly predictions into orbital planning tools to minimize disruption risks as the magnetic dent continues to grow.
The African Connection: A Deep-Time Mystery
The link between the South Atlantic Anomaly and the African continent’s deep mantle structure could hold key clues to Earth’s magnetic future. The African LLSVP is a colossal zone of hot, dense material extending thousands of kilometers upward from the core-mantle boundary.
This structure is one of two enormous “blobs” inside Earth — the other sits under the Pacific Ocean — and both appear to interfere with convection at the core boundary. Scientists theorize that the African blob in particular may be slowing or redirecting the flow of molten iron under the South Atlantic, leading to those strange reversed flux patches that are weakening the field.
This behavior isn’t new, though; geological data suggest that weak-field regions similar to the current South Atlantic Anomaly have existed multiple times in Earth’s history. We’re just lucky enough — or unlucky enough — to be alive during one of its growth phases.
Looking Ahead
While humanity isn’t in real danger from the anomaly itself, the trend is scientifically profound. It underscores how dynamic and unpredictable our planet’s inner workings truly are.
The latest observations show that since 2014, the SAA’s weak-field area has expanded by roughly half the size of continental Europe and now encompasses nearly 1% more of Earth’s surface. The lowest measured intensity has dropped from about 22,430 nanoteslas to 22,094, a steady but significant decline that reveals how quickly magnetic flux can shift.
As Finlay and his team continue to analyze Swarm’s data, they hope to refine computer models of how turbulence in Earth’s molten core drives these field changes. Better models could eventually allow scientists to forecast geomagnetic fluctuations — essential not only for space technology but also for understanding how our planet’s internal dynamics evolve over time.
The Bottom Line
Earth’s magnetic field isn’t fading away anytime soon, but it’s definitely acting weird. With the South Atlantic Anomaly expanding eastward and deep structures influencing it from below, our planet’s magnetic personality seems more chaotic than steady.
Fortunately, missions like ESA’s Swarm are giving scientists a front-row seat to Earth’s inner engine at work. And as Stromme put it, “It’s really wonderful to see the big picture of our dynamic Earth.”
For now, this growing dent in our magnetic armor may just be a reminder that the forces shaping our world — even the invisible ones — are far from static.
