A Growing Weak Spot in Earth’s Magnetic Field May Cause More Satellites to Short Circuit

The Earth’s magnetic field is like an encompassing shield, primarily deflecting charged particles launched from the sun. But this shield is not perfect; it has weak spots that leave openings for cosmic radiation, sometimes putting satellites in danger.

One of these vulnerable areas is the South Atlantic anomaly, a weak point in the magnetic field that has been growing for more than a decade.

A new study published in Earth physics and planetary interiors shared a snapshot of the expansion of the South Atlantic anomaly, revealing that it has grown by an area nearly half the size of continental Europe since 2014. This and other trends in the magnetic field show how important it is to track Earth’s ever-changing magnetism.

Earth’s magnetic field

The South Atlantic Anomaly (SAA), located over South America and the South Atlantic Ocean, was first identified in the 19th century. Since then, researchers have taken a close interest in the changes it has undergone over time. Indeed, the SAA is one of the main areas where satellites in low Earth orbit are exposed to significant doses of cosmic radiation, which can cause structural damage and electronic malfunctions.

The SAA exists in part because of Earth’s tilt and the complex processes that shape the magnetic field, involving the flow of molten metals in the planet’s outer core. Another major factor is the SAA’s proximity to Earth’s inner Van Allen belt.

The Van Allen belts are two donut-shaped zones that wrap around Earth, trapping particles from cosmic rays or solar wind. The SAA is where the inner Van Allen Belt reaches closest to the Earth’s surface, causing the area to be flooded with charged particles.

Learn more: Van Allen belts are dangerous radiation rings in space – here’s how astronauts get past them

A weak point in the Earth’s magnetic field

The new study traced the growth of the SAA using satellite data recorded as part of the European Space Agency’s Swarm mission. The mission, launched in 2013, includes three identical satellites (Alpha, Bravo and Charlie) which measure magnetic signals emitted from the planet.

The satellites observed steady growth in the SAA from 2014 to 2025. They also spotted a particular region – over the Atlantic Ocean, southwest of Africa – where the weakening of the magnetic field has been particularly significant since 2020.

“The South Atlantic anomaly is not just one block,” lead study author Chris Finlay, a professor of geomagnetism at the Technical University of Denmark, said in a statement. “Things are developing differently towards Africa and towards South America. Something special is happening in this region which is weakening the sector more intensely.”

The pronounced attenuation is associated with areas of reverse flux, phenomena that represent atypical movement of magnetic field lines. These lines normally originate from the Earth’s core in the Southern Hemisphere, but in the SAA they return to the core. Currently, reverse flow phenomena are moving westward over Africa, according to the researchers.

The dynamic magnetism of the Earth

The SAA is not the only place where the Earth’s magnetic field is undergoing changes. The new study also examined fluctuations in two areas of the Northern Hemisphere where the magnetic field is particularly strong.

One of them is over Siberia, where the region of intense fields has increased by 0.42% of Earth’s area (about the size of Greenland). The other is in Canada, where the intense field region has shrunk by 0.65% of the Earth’s area (about the size of India).

According to the researchers, the growth of the magnetic field over Siberia is linked to the drift of the north magnetic pole towards this area, which will continue to impact navigation systems in the years to come.

Learn more: The magnetic North Pole is drifting across the Arctic towards Siberia

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