The field is looping back into the core instead of radiating outward
Beneath the South Atlantic, Earth's magnetic field is quietly thinning — a phenomenon known as the South Atlantic Anomaly has expanded by nearly half the size of continental Europe since 2014, now stretching a new arm toward Africa where the weakening is most severe. Driven by reverse flux patches migrating deep within the planet's molten outer core, this ancient and restless process has moved from scientific curiosity to operational concern, as satellites and spacecraft passing through the region face increasing exposure to solar radiation and the risk of system failure. The planet's magnetic architecture, long assumed to be stable on human timescales, is reminding us that Earth remains a dynamic and unfinished world.
- A weak spot in Earth's magnetic shield has grown dramatically, now rivaling nearly half the landmass of continental Europe — and it is still spreading.
- A newly formed lobe is pushing eastward toward Africa, where the magnetic field is weakening faster than anywhere else on the planet.
- Satellites passing through the anomaly descend into a zone where the protective field drops from 400 miles above Earth's surface to just 120, leaving hardware vulnerable to radiation-induced malfunctions and blackouts.
- Deep beneath the South Atlantic, reverse flux patches in the molten outer core are migrating and expanding, acting as the hidden engine behind the anomaly's rapid growth.
- Researchers using the European Space Agency's Swarm satellites are tracking these shifts in near real-time, racing to understand a system whose full trajectory remains uncertain.
- With Earth's northern magnetic pole also drifting toward Siberia and field strengths shifting across Canada and Russia, scientists warn that the planet's magnetic landscape is in a period of significant and consequential transformation.
Beneath the South Atlantic Ocean, Earth's magnetic field has been quietly retreating. The South Atlantic Anomaly — a weak spot in the planet's protective shield first documented in the 19th century — has expanded over the past decade to nearly the size of continental Europe, and has now sprouted a new lobe reaching toward Africa, where the weakening is most intense.
Within the anomaly's boundaries, the magnetic field that normally hovers some 400 miles above Earth's surface dips to just 120 miles — a dramatic thinning that leaves satellites and spacecraft dangerously exposed to solar radiation, charged particles, and the hardware failures that follow. What was once a scientific curiosity has become a matter of operational urgency for the infrastructure orbiting overhead.
Chris Finlay, a geomagnetism professor at the Technical University of Denmark and lead author of a new study published in Physics of the Earth and Planetary Interiors, describes the anomaly as something far more complex than a simple weak patch. The field is behaving differently near Africa than near South America, he notes, suggesting something unusual is unfolding in that region specifically. The cause lies roughly 1,900 miles below the surface, in Earth's molten outer core, where so-called reverse flux patches — areas where the magnetic field loops back into the core rather than radiating outward — are migrating and expanding, driving the anomaly's eastward spread.
Finlay's team tracked these changes using data from the European Space Agency's Swarm mission, a trio of satellites measuring Earth's magnetic signals since 2013. Their findings reveal a planet in motion: a reverse flux patch has been migrating westward over Africa, intensifying the field's decline in that direction, while the anomaly itself has grown by an area nearly half the size of continental Europe in just eleven years.
The South Atlantic is not alone in its transformation. The magnetic field above Canada has weakened and contracted, while above Siberia it has strengthened and grown — changes linked to the ongoing migration of Earth's northern magnetic pole toward Russia. The full implications of these shifts remain uncertain, and scientists emphasize that continued satellite monitoring is not merely academic. As the anomaly expands and the planet's magnetic architecture continues to evolve, understanding what lies ahead has become a matter of practical necessity.
Beneath the surface of the South Atlantic Ocean, something is shifting. A weak spot in Earth's magnetic field—a region scientists call the South Atlantic Anomaly—has been growing for over a decade, and satellite data now shows it has expanded to nearly the size of continental Europe. More troubling still, it has sprouted a new lobe extending toward Africa, where the magnetic field is weakening faster than anywhere else on the planet.
The anomaly was first documented in the 19th century, but its recent acceleration has caught the attention of researchers studying Earth's deep interior. Within the anomaly's boundaries, the protective magnetic field that normally hovers about 400 miles above Earth's surface dips down to just 120 miles—a dramatic thinning that exposes anything passing overhead to dangerous solar radiation and charged particles. For satellites and spacecraft, this is a serious problem. The magnetic field acts as a shield, deflecting harmful X-rays, ultraviolet radiation, and energetic particles streaming from the sun. When that shield weakens, hardware can malfunction, systems can fail, and communications can black out.
Chris Finlay, a geomagnetism professor at the Technical University of Denmark and lead author of a new study on the phenomenon, describes the anomaly as far more complex than a simple weak patch. "It's changing differently towards Africa than it is near South America," Finlay explained. "There's something special happening in this region that is causing the field to weaken in a more intense way." The research, published in Physics of the Earth and Planetary Interiors, reveals that the anomaly is not static—it is actively spreading eastward, driven by unusual activity deep within the planet.
The culprit lies roughly 1,900 miles beneath Earth's surface, in the outer core. This vast ocean of molten iron generates the planet's magnetic field through the movement of liquid metal and the electrical currents it produces. Normally, magnetism generated in the core flows outward, creating the protective field that extends through the atmosphere. But beneath the South Atlantic, something different is happening. In certain areas, the magnetic field is looping back into the core instead of radiating outward—a phenomenon called reverse flux patches. These patches are not stationary. They migrate and expand, and their movement explains why the South Atlantic Anomaly has grown so dramatically since 2014.
Finlay and his team tracked these changes using data from the European Space Agency's Swarm mission, which deploys three identical satellites to measure magnetic signals from Earth's interior and oceans. The satellites have been monitoring the planet's magnetic field since 2013, and the data they collected reveals a planet in flux. Over the past decade, a reverse flux patch has been moving westward over Africa, intensifying the weakening of the magnetic field in that direction. Meanwhile, the anomaly itself has expanded by an area nearly half the size of continental Europe—a staggering transformation in just eleven years.
The South Atlantic is not the only region showing dramatic change. Above Canada, the magnetic field has weakened slightly, and the strong region there has shrunk by an area nearly the size of India. Above Siberia, by contrast, the field has strengthened, with the strong region growing by an area the size of Greenland. Researchers attribute these shifts to a migration of Earth's northern magnetic pole toward Siberia, a movement that has been underway for several years. But the full implications of these changes remain unclear. The dynamics are still evolving, and scientists emphasize the need for continued monitoring to understand what comes next.
For the satellites and spacecraft that depend on Earth's magnetic shield, the stakes are high. As the South Atlantic Anomaly continues to expand and intensify, the risk to orbital infrastructure grows. Understanding how and why these deep planetary processes are unfolding has become not just a matter of scientific curiosity, but of practical necessity.
Citas Notables
The South Atlantic Anomaly is not just a single block. 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.— Chris Finlay, geomagnetism professor, Technical University of Denmark
La Conversación del Hearth Otra perspectiva de la historia
Why does a weak spot in the magnetic field matter to anyone who isn't a physicist?
Because satellites rely on that field for protection. When the field weakens, radiation gets through, and satellites malfunction or fail. That affects GPS, weather forecasting, communications—things people depend on every day.
So this anomaly has been around since the 1800s. What's different now?
It's growing much faster than it used to. Since 2014, it's expanded by an area nearly half the size of continental Europe. And it's sprouting a new lobe toward Africa where the weakening is most intense. That's the alarming part.
What's causing it to grow?
Deep in Earth's outer core, there are patches where the magnetic field is reversing—looping back into the core instead of flowing outward. These patches are moving and expanding. One is migrating westward over Africa, intensifying the weakness there.
Can we stop it?
No. This is driven by the movement of molten iron 1,900 miles beneath the surface. We can't control that. What we can do is monitor it closely and prepare our satellites and infrastructure for the risks.
How long has this been happening?
The anomaly itself was first detected in the 1800s, but the rapid expansion is recent—mainly since 2014. Scientists are still trying to understand whether this is a temporary fluctuation or part of a longer pattern.
What happens if it keeps growing?
More satellites will pass through weaker magnetic field, exposing them to more radiation. That means more potential for hardware failures, blackouts, and loss of critical services. It's why continued monitoring is so important.