By Sarah Cope | 2025-12-09

New satellite observations show that a weak region in Earth’s magnetic field known as the South Atlantic Anomaly is widening, exposing satellites, spacecraft and scientific instruments that pass through it to increased radiation.

This can lead to malfunctions or damage to critical hardware, and even blackouts, according to the European Space Agency (ESA).

The latest assessment, made using 11 years of magnetic field measurements from the ESA's Swarm satellite constellation, offers a clearer understanding of how the anomaly has evolved.

The constellation's three satellites measure magnetic signals from Earth’s core, mantle, crust and oceans, as well as from the ionosphere and magnetosphere, according to the ESA.

This data is helping scientists understand what the magnetic field’s growth may indicate about its long-term behavior, with the newest findings published in the Physics of the Earth and Planetary Interiors journal in October.

Earth’s magnetic field forms through the motion of molten iron within its outer core, which creates electric currents that build a magnetic shield around the planet. This blocks many charged particles from the sun and from deep space.

When the field weakens, the higher radiation exposure can damage sensitive electronics, casing them to glitch, reset or, in severe cases, fail.

The anomaly was first identified in the 19th century through measurements by early geomagnetic observatories. Today, it extends across a broad region southeast of South America and toward the southwest coast of Africa.

In this zone, the magnetic field dips closer to Earth’s surface. Modern satellites crossing the area often power down instruments to avoid damage.

The International Space Station (ISS) also experiences higher radiation doses when its orbit carries it through this region.

Monitoring magnetic signals

Since the Swarm constellation began monitoring magnetic signals in 2014, the South Atlantic Anomaly has grown to cover almost two million square miles, and also shows subtle shifts in strength and shape.

The field is weakening in different ways across the region, according to the new study's lead author Chris Finlay, a professor of geomagnetism at the Technical University of Denmark who works with the Swarm mission.

Near Africa, the decline shows a distinct pattern, compared with the portion of the magnetic field near South America. These variations point to separate processes at work inside Earth's core, highlighting its dynamic nature.

Understanding the contrast may help scientists refine models of the geodynamo, the mechanism that maintains the magnetic field.

The anomaly's growth has raised questions about whether this might signal an impending magnetic pole reversal, though current evidence does not show that such a reversal is under way.

Magnetic poles have flipped many times in Earth’s history, but the process takes thousands of years, and researchers caution that short-term shifts in the anomaly, though significant, do not indicate immediate global change.

They note that continued monitoring will help scientists track its evolution and assess how it may influence future missions in orbit.

As more satellites enter low Earth orbit, radiation-related faults will remain a concern. Mission planners may need to schedule protective measures when a spacecraft approaches the anomaly.

Engineers may also need to design more resilient electronic components for satellites that operate in high-risk zones.