Unlocking Earth’s Secrets: How Satellites Uncover a Growing Weakness in Our Magnetic Field

There’s an intriguing change happening in the Earth’s magnetic field over the South Atlantic Ocean. Recent satellite data reveals that a weak spot, known as the South Atlantic Anomaly, is expanding. This discovery comes from over ten years of observations by the European Space Agency’s Swarm satellites.

The magnetic field is vital for protecting the Earth from harmful cosmic radiation and solar particles. Scientists believe its source lies in the outer core, where molten iron creates electrical currents that generate this shield.

First identified in the 1800s, the South Atlantic Anomaly is located southeast of South America and southwest of Africa. Here, the magnetic field dips lower, resulting in satellites receiving more radiation. This can cause technical glitches and even temporary blackouts.

From 2014 to 2025, Swarm satellites meticulously tracked the magnetic signals in this area. They found that the anomaly has grown to about two million square miles, nearly half the size of continental Europe. Curiously, since 2020, the weakening of this field has sped up, with different regions changing at varying rates. According to Chris Finlay, a geomagnetism expert from the Technical University of Denmark, this region behaves unusually, with variations noticed between areas near Africa and South America. “It’s changing differently towards Africa than it is near South America,” he noted.

Finlay also explained that magnetic field lines from the core seem to be bouncing back into it, but the reason behind this remains unclear. This phenomenon is contributing to the area’s weakening.

Interestingly, Swarm satellites discovered other magnetic changes as well. In the southern hemisphere, there’s a strong magnetic field region, while two more anomalies exist in the northern hemisphere: one near Canada and the other over Siberia. The Canada anomaly has decreased in size—about the size of India—while the Siberian one has nearly doubled, now the size of Greenland.

Looking ahead, the ESA plans to continue monitoring the magnetic field. Anja Stromme, the Swarm Mission manager, expressed excitement about the ongoing discoveries, especially as the data from the satellites will extend beyond 2030, coinciding with the solar minimum—a time expected to reveal even more about our dynamic Earth.

Keep an eye on this space. The changes in our magnetic field not only affect technology but might also provide insights into Earth’s interior dynamics and how our planet interacts with the vast cosmos around it.

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European Space Agency, Space