The Earth's magnetic field is like an all-encompassing shield, mainly reflecting charged particles emitted by the Sun. But this shield is not flawless; it has weaknesses that leave room for exposure to cosmic radiation, sometimes putting satellites in danger.
One such vulnerable zone is the South Atlantic Anomaly, a bright weak spot in the magnetic field that has been growing steadily for more than a decade.
new study published in Physics of the Earth and planetary interiors shared a snapshot of the expansion of the South Atlantic Anomaly, showing that since 2014 it has grown by almost half the area of continental Europe. This and other trends in the magnetic field show how important it is to keep up with the 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 paid close attention to the changes it has undergone over time. This is because SAA is one of the main areas where satellites Those in low Earth orbit are exposed to significant doses of cosmic radiation, which can lead to structural damage and electronic malfunction.
The SAA exists in part because of the Earth's tilt and the complex processes that shape the magnetic field, including the flow of molten metals in the planet's outer core. Another important factor is the proximity of SAA to Earth's inner Van Allen belt.
Van Allen belts These are two donut-shaped zones that surround the Earth, trapping particles from cosmic rays or solar wind. The SAA is where the inner Van Allen belt comes closest to the Earth's surface, causing the area to be flooded with charged particles.
Read more: Van Allen belts – dangerous radiation rings in space: how astronauts overcome them
Weak spot in the Earth's magnetic field
A new study traced the growth of SAA using satellite data that was recorded by the European Space Agency's Swarm mission. The mission, launched in 2013, includes three identical satellites (Alpha, Bravo and Charlie) that measure magnetic signals emitted by the planet.
Satellites saw steady growth in SAA from 2014 to 2025. They also found a specific region – over the Atlantic Ocean southwest of Africa – where the weakening of the magnetic field has been particularly noticeable since 2020.
“The South Atlantic Anomaly is not just one block,” said study lead author Chris Finley, professor of geomagnetism at the Technical University of Denmark, in his report. statement. “It changes differently in Africa than near South America. There's something special going on in that region that causes the field to weaken more intensely.”
The pronounced weakening is associated with backflux spots, phenomena that represent atypical movement of magnetic field lines. These lines usually emerge from the Earth's core in the southern hemisphere, but in South Africa they return to the core. Right now, elements of the reverse flow are moving west over Africa, the researchers say.
Dynamic magnetism of the Earth
South Africa is not the only place where the Earth's magnetic field is experiencing 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 the strong field has increased by 0.42 percent of the Earth's surface area (about the size of Greenland). The other is over Canada, where the strong field region has shrunk by 0.65 percent of the Earth's surface area (about the size of India).
The growth of the magnetic field over Siberia, the researchers say, is associated with north magnetic pole is drifting into this area, which will continue to affect navigation systems in the coming years.
Read more: The North Magnetic Pole drifts across the Arctic towards Siberia
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