Scientists have long known that Earth’s magnetic field isn’t perfectly even. In recent decades, however, they’ve noticed an unusual weak spot growing over the South Atlantic Ocean. This region, named the South Atlantic Anomaly (SAA), marks where Earth’s magnetic field dips lower than anywhere else on the planet.
Scientists first detected the anomaly in the late 1950s, when unexpected radiation exposure was recorded by satellites orbiting South America. Even though the anomaly has been known for many decades, scientists have only recently been able to track how rapidly it’s changing. Recent measurements have shown that the anomaly’s area has almost doubled since its discovery, and its field strength continues to weaken. According to Sci.News, the SAA is still drifting westward at roughly 20 kilometers per year, raising questions about what’s happening deep inside the Earth.
Earth’s magnetic field is generated by the continuous motion of the molten metals that lie in the planet’s outer core. These metals are mostly iron and nickel. Above the South Atlantic, roughly between Argentina and southern Africa, that shield grows thinner. In that stretch of sky, radiation can penetrate much closer to Earth, disrupting spacecraft that pass through. Engineers have recorded data corruption on Swarm satellites whenever they cross the region, according to ESA. To prevent damage, most spacecraft either automatically suspend their observations during each pass or take extra precautionary measures.
“Even though the SAA is slow-moving, it is going through some change in morphology, so it’s also important that we keep observing it by having continued missions,” Dr. Terry Sabaka, a research assistant at NASA’s Goddard Space Flight Center, said.
According to Universe Magazine, the latest evidence shows the anomaly may even be splitting in two—one lobe centered over South America and another forming near southern Africa.
Scientists trace the anomaly’s origin thousands of miles below the surface. Deep beneath southern Africa lies a massive region called the African Large Low Shear Velocity Province, a dense zone at the boundary between the planet’s solid mantle and molten outer core. Researchers believe it disturbs the flow of liquid iron that powers the magnetic field. This disruption creates reverse flux patches, where instead of extending outward, the magnetic field lines turn back toward the core. Over time, those reversals weaken the field above them, forming the South Atlantic Anomaly we see today.
Despite its steady growth, experts say the anomaly is not a cause for alarm. According to The Times of India, the anomaly normally does not pose any threat to life on Earth. However, the SAA does serve as a challenge for space safety. As reported by the ESA, technology used in space—such as satellites—is exposed to much higher amounts of radiation when passing over the region.
For now, the dent in Earth’s magnetic field remains a reminder that our planet is still geologically active deep within. Studying it may even help scientists predict how magnetic fields evolve. Although the magnetic field of our planet is proving far more complex than we once thought, it offers both an opportunity and a challenge to understand how our planet really works.
