New Delhi: A weak region in Earth’s magnetic field, called the South Atlantic Anomaly, has expanded by an area roughly half the size of continental Europe
over the past decade. This region, located between South America and Africa, has puzzled scientists for years. Now, new findings from the European Space Agency’s Swarm satellites show that the anomaly has not only grown but is weakening faster than before, especially toward Africa.
Researchers say this change could have major implications for satellites and astronauts passing over the area. Earth’s magnetic field acts like a shield, protecting the planet from harmful solar radiation. When that shield weakens, spacecraft and electronic systems become more vulnerable.
Eleven years of Swarm satellite observations | Source: https://doi.org/10.1016/j.pepi.2025.107447
What exactly is the South Atlantic Anomaly?
The South Atlantic Anomaly, first identified in the 19th century, is an unusually weak spot in the planet’s magnetic field. Normally, Earth’s field acts as an invisible barrier that blocks charged particles from the Sun. But over this region, the protection is thinner, allowing more radiation to reach low-Earth orbit.
For satellites and the International Space Station, that means higher exposure to radiation. This can disrupt electronics, damage instruments, or cause brief communication blackouts. In simple terms, when satellites pass over the anomaly, it’s like driving through a storm of invisible high-energy particles.
According to ESA’s Swarm satellite data, this weak zone has been expanding since 2014. Lead researcher Chris Finlay, professor of geomagnetism at the Technical University of Denmark, said that the field isn’t weakening evenly. It’s changing more rapidly over Africa compared to South America.
What’s happening beneath the surface?
The cause of this magnetic oddity lies deep inside Earth , around 3,000 kilometers below the surface, where molten iron churns inside the outer core. This constant motion generates powerful electrical currents, which create our planet’s magnetic field.
But beneath the South Atlantic Anomaly, scientists have discovered “reverse flux patches”, strange regions where the magnetic field behaves in the opposite direction. Instead of lines of magnetic force flowing out from the core, they sink back in. Finlay explained that one of these regions is moving westward under Africa, making the anomaly even weaker in that area.
The field is not collapsing, it’s shifting
Interestingly, not all parts of Earth are losing magnetic strength. The same Swarm data shows that while the field weakens over the South Atlantic, it is strengthening over Siberia , by an area roughly the size of Greenland. Meanwhile, the once-strong magnetic region over Canada has shrunk by nearly the size of India.
This uneven shift is also linked to the magnetic north pole’s migration toward Siberia, a trend that began in the mid-19th century and continues today. Since navigation systems like compasses rely on magnetic north, such shifts can affect everything from smartphone maps to aircraft orientation.
Why Swarm’s data matters
The Swarm satellite constellation, launched in November 2013 from Russia’s Plesetsk Cosmodrome, has provided the longest continuous record of Earth’s magnetic field from space. Over the last 11 years, the three satellites have tracked subtle changes in magnetism from the planet’s core to its outer atmosphere.
ESA’s mission manager Anja Stromme said the extended dataset allows scientists to see the “big picture” of our planet’s dynamic magnetic field. The agency plans to continue the Swarm mission beyond 2030 to gather more insights, especially during the next solar minimum.
Why this matters for everyone
While the South Atlantic Anomaly doesn’t pose any direct threat to life on the ground, it’s a growing concern for the space industry. With hundreds of satellites orbiting Earth, from weather trackers to Starlink internet nodes, even brief radiation spikes can lead to malfunctions or data loss.
