Earth’s magnetic field is a silent shield, an invisible force that deflects solar particles and cosmic radiation. Without it, life on the surface would be impossible. But that shield is not static: it changes, deforms and sometimes weakens.
Three thousand kilometers underground, in the outer core of the planet, an ocean of molten iron spins like a dynamo. Its movement generates electrical currents that feed the global magnetic field. It is a complex system, so delicate that a slight variation in the speed or composition of that fluid can alter the entire balance.
And that, precisely, seems to be happening now.
The anomaly that grows under the Atlantic
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Since 2013, a fleet of three European satellites – the Swarm mission – has monitored the behavior of the magnetic field. Their data, analyzed over more than a decade, reveals a disturbing pattern: a region of weak field stretching over the South Atlantic, right between South America and Africa.
Scientists have named it the South Atlantic Anomaly. In eleven years, its size has doubled, reaching an area almost equivalent to half of Europe.
In that region, satellites orbiting at low altitudes suffer from electronic failures, spontaneous reboots, or signal loss. Even astronauts passing through the area aboard the International Space Station may be exposed to higher doses of radiation.
What happens under our feet
The new study, published in Physics of the Earth and Planetary Interiors, suggests that the origin of the phenomenon is much lower, on the border between the liquid outer core and the rocky mantle of the planet.
There, the molten iron currents seem to behave anomalously. Researcher Chris Finlay, from the Technical University of Denmark, describes it this way: “Normally, magnetic field lines leave the core in the southern hemisphere. But under the South Atlantic Anomaly we see areas where the field, instead of leaving, returns towards the core.”
That is, the Earth’s magnetic shield is not only weakening: it is locally reversing. A phenomenon that could alter the trajectory of the charged particles and explain the increase in radiation in the area.
A field that moves and mutates
The researchers also noted that the anomaly is not a fixed block. One of its weaker zones is slowly moving westward over Africa, while the field strengthens over Siberia and weakens over Canada.
This constant displacement affects navigation, communications and satellite observation systems. The dynamics between regions of strong and weak magnetism can modify the way satellites receive radiation, increasing the risk of electronic damage.
“It is a process that we do not fully understand, but the data suggests that the Earth’s magnetic field is more unstable than we believed,” concludes Finlay.
A prelude to something bigger?
Scientists do not rule out that this weakening is part of a natural cycle. The Earth’s magnetic field has reversed multiple times in the past: what is now magnetic north was once south. But these processes usually take thousands of years.
For now, the concern is not the end of the world, but the immediate effects: satellite failures, interruptions in GPS systems and increasing exposure to radiation in low orbit.
The South Atlantic Anomaly is, in a way, a reminder that the planet is still alive, breathing molten iron under our feet. And that heart, although invisible, sets the pace of our technological survival.
