EARTH, Laniakea Supercluster—Every satellite orbiting Earth knows about the South Atlantic Anomaly, even if most humans don’t. It’s a massive dent in the planet’s magnetic shield where radiation leaks through like sunlight through a cracked windshield, frying electronics and glitching hardware on anything that passes overhead.

Now, new data from the European Space Agency’s Swarm mission shows that dent has ballooned by an area nearly half the size of Europe in just over a decade. This change, scientists say, hints at something strange happening thousands of miles beneath our feet, in the restless liquid iron that powers Earth’s magnetic “force field,” keeps our atmosphere intact, and makes this rock habitable.

The findings, published in Physics of the Earth and Planetary Interiors and based on 11 years of observations from the European Space Agency's Swarm satellite constellation paint a picture of a planet whose magnetic armor is unsettlingly shifting in real time. One section of the anomaly, located southwest of Africa, has started weakening even faster since 2020.

"The South Atlantic Anomaly is not just a single block," said Chris Finlay, Professor of Geomagnetism at the Technical University of Denmark and lead author of the study, in a statement published by ESA.

"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."

First identified in the 19th century off the southeast coast of South America, per ESA's reporting, the South Atlantic Anomaly is a massive indentation on a region where the protective magnetic field is significantly weaker than the global average. If Earth's magnetism were body armor, this would be the spot where the plates don't overlap.

It matters most for anything in orbit. Satellites that pass through the anomaly get hit with elevated radiation levels, which according to ESA can cause hardware malfunctions, data corruption, and even temporary blackouts. The International Space Station's trajectory takes it through the region regularly, and astronauts passing overhead have reported seeing flashes of light, thought to be cosmic rays striking their retinas.

Deep Earth Is Getting Weird

The culprit behind the anomaly's growth lies roughly 3,000 kilometers (1,860 miles) below the surface, in the roiling ocean of liquid iron that makes up Earth's outer core. That molten metal generates the planet's magnetic field through a process loosely analogous to a dynamo. But the flow patterns aren't uniform, and scientists have identified features called "reverse flux patches"—areas at the core-mantle boundary where the magnetic field essentially runs backward.

"Normally we'd expect to see magnetic field lines coming out of the core in the southern hemisphere. 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," Finlay explained.

One of these reverse flux patches is currently migrating westward over Africa, which Finlay says is directly contributing to the accelerated weakening in that part of the anomaly.

The North Pole Keeps Drifting

The South Atlantic isn't the only place where Earth's magnetic geography is being redrawn. According to the same Swarm dataset, the strong magnetic field region over Canada has shrunk by 0.65 percent of Earth's surface area (nearly the size of India) while the corresponding region over Siberia has expanded by 0.42%, an area comparable to Greenland. These figures come from ESA's analysis of the Swarm mission data.

This tug-of-war is linked to the ongoing migration of the magnetic north pole toward Siberia, a shift that already forced an early update to the World Magnetic Model used by navigation systems worldwide.

"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 said. "It's only by having satellites like Swarm that we can fully map this structure and see it changing."

Should You Panic?

Probably not, but maybe? The South Atlantic Anomaly doesn’t mean Earth’s magnetic field is about to collapse or that a full pole reversal is imminent, although the field has flipped hundreds of times in the geological record (the last major reversal—the Brunhes–Matuyama event—took place about 780,000 years ago). What the new data does confirm is that the field is far more dynamic and unpredictable than most people assume, and that monitoring it closely is no longer optional.

The Swarm satellites, launched in November 2013, now hold the longest continuous space-based record of Earth’s magnetic field—a dataset that will only grow more valuable as the anomaly continues to evolve.

Whatever is churning thousands of miles beneath the Atlantic, it isn't slowing down. And neither, hopefully, is our ability to watch it.