Scientists Track Expansion of Earth’s Magnetic Weak Spot

By Ruha Lee, Haram Kim

Earth's magnetic field is an invisible force that surrounds the planet, produced by the convective movement of molten nickel and iron in the outer core. When these metals move and spin, they generate electric currents, which produce magnetism. Earth thus operates as a giant bar magnet with a magnetic north and south pole. The magnetic field extends outward into space far enough to make a region called the magnetosphere that is able to repel charged particles from the Sun. On the surface, it influences navigation and technology. A good representation would be compasses. Compasses point towards the north because of it, and many animals, such as birds and sea turtles, use it to orient themselves over large distances. The magnetic field is always changing as a result of the flowing and shifting of the liquid metal inside the core, which shifts the poles slowly over time and alters the field strength throughout the world.

However, as much as it provides protection to us,without it, the results would be lethal. It would only be a matter of time until the planet faced impending problems. A good portion of that would be being strafed directly by the solar wind. A steady stream of charged particles emitted from the Sun would abrade Earth on every side. The particles would erode away portions of the atmosphere, thinning it, and allowing more deadly radiation to reach the surface of our planet. The extra radiation would mean more detrimental harm to living cells. It would also dramatically shift the climate causing the environment to become uninhabitable for most life forms. The loss of the field's protection would also unprecedentedly impact human technology. As satellites, power grids, and communications would be exposed to solar variability their protection would no longer be in use. In addition, compasses would be obsolete in pointing north, and most animals that make magnetic navigational cues would become disoriented while migrating. The changes over long periods would cause serious deformities to Earth's atmosphere and climate, ultimately transforming the conditions that our current life depends on.

Swarm is a low Earth orbit satellite constellation for communication which consists of three European Space Agency satellites that were launched in 2013 to monitor Earth’s magnetic field more closely. Two of the satellites fly together at a low altitude and a third satellite follows them in a higher orbit. This formation provides scientists with a three-dimensional dataset to better understand the behavior of Earth's magnetic field and how its chronological flux. Each satellite has highly sensitive instruments; the satellites have magnetometers to measure magnetic field strength and direction, accelerometers to detect the small movements of their orbits, and sensors to measure electric fields from charged particles in the upper part of Earth's atmosphere. By triangulating data from all three spacecraft, the scientists can extract the magnetic signals from a range of sources, including data from the core, mantle, crust, oceans, ionosphere, and magnetosphere that shape Earth's magnetic field. With precise measurements, scientists can better understand the complex systems that generate and affect the magnetic field.

The Swarm mission exists and is still demanded today because the magnetic field is essential for life and modern technology. According to the European Space Agency (ESA), the field has been weakening over the past few centuries. With scientists needing to accurately analyze and use long-term data to understand why it is weakening, the anomalies continue to grow. The Swarm mission takes measurements of even small changes in both the strength and direction of the field. In particular, they will be able to measure exactly how liquid metal flows in the outer core that gives rise to the magnetic field, and how that flowing behavior translates to magnetic pole reversals or shifts. The Swarm technology also offers protection to humans, designing satellites to provide better accuracy to satellite navigation and communication systems and creating forecast models for geomagnetic storms that can rip apart power grids. Besides the practical implications of the Swarm mission, we also expect to improve scientific understanding of the physical processes that apply to our planet and perhaps sustain the invisible magnetic field around and protecting Earth.

Thanks to Swarm, scientists are able to discover anomalies. One of the most unsettling changes took shape over the South Atlantic. What began as a quiet dip in magnetic strength has spread across the ocean like a dark stain, now stretching over an area nearly half the size of continental Europe. Scientists call it the South Atlantic Anomaly, and in recent years, it has revealed something new: a second, fainter patch emerging off the coast of southern Africa. The anomaly, it seems, is no longer just growing. It is evolving.

Beneath these regions, deep in the planet’s churning outer core, researchers have found reverse flux patches- places where the magnetic field folds inward, diving back toward the molten iron heart of the Earth. These hidden eddies appear to be driving the anomaly’s expansion. And while this weak spot grows, the field over Siberia has strengthened, as if magnetic energy were being pulled from one part of the planet and quietly gathered in another.

According to the National Aeronautics and Space Administration (NASA), the stakes are more tangible than they might seem. When the magnetic field thins, the shield that protects satellites and spacecraft from high-energy radiation weakens too. Systems falter, instruments glitch, missions are put at risk. Even the International Space Station alters its routines when crossing the anomaly’s boundaries. Swarm’s constant watch gives scientists a way to keep pace with these changes- and, just as importantly, to anticipate what might come next.

The anomaly itself is not a modern creation. It stems from the uneasy tilt between Earth’s magnetic and rotational axes, amplified by the turbulent movement of molten iron deep underground. But over the past two centuries, the anomaly has been steadily intensifying. Satellites flying through the region often shut down sensitive instruments, like travelers closing their umbrellas in a sudden storm. 

At the core of it all lies the geodynamo, the restless engine of Earth’s magnetism. Molten iron, swirling in slow, powerful currents, generates electric fields that, together, form the shield around our planet. Swarm’s data show that the strength of this dipole field has dropped by about 10 percent since the mid-1800s. This isn’t a uniform fading- it’s concentrated over the South Atlantic, shaped by shifting core flows, reverse flux patches, and perhaps subtle variations in heat along the boundary between the mantle and the core.

Earth’s magnetic field has always been restless. Over millions of years, it has weakened, shifted, and even flipped entirely, its poles wandering across the globe before settling again. But this moment is different. The field is changing quickly, and human technology has grown fragile in ways nature never had to account for before.

There’s no sign that a pole reversal is looming, but scientists see the South Atlantic Anomaly as a rare window into the hidden machinery of the planet. Every orbit of Swarm’s satellites offers another clue, another trace of how the magnetic shield bends and breathes. The story is still being written, not in words, but in invisible lines that sweep across the sky- and in the quiet hum of a force that has protected life on Earth for billions of years.