The Earth’s invisible shield is showing signs of strain. A vast weak spot in the planet’s magnetic field, located over the South Atlantic Ocean, has expanded rapidly in the past decade, sparking concern among scientists studying its unusual behaviour.
What did scientists discover about the anomaly?
According to satellite data, the region known as the South Atlantic Anomaly has grown by an area nearly half the size of continental Europe since 2014. The weakened zone has also developed a new lobe toward Africa, where the magnetic field is deteriorating the fastest.
The findings, published in the November issue of Physics of the Earth and Planetary Interiors, show how changes deep within Earth’s outer core are reshaping its magnetic field. Researchers warn that this could pose a risk to satellites and spacecraft that pass through the region.
What causes the magnetic field to weaken?
Earth's magnetic field is formed by its outer core, an agitated sea of molten iron roughly 3,000 kilometres below the planet's surface. The motion of the molten metal generates electrical currents that create the planet's magnetic field, which radiates outward into space and shields Earth from solar radiation.
But evidence indicates that in other areas of the South Atlantic, magnetic lines are looping into the core instead of pushing out. Such "reverse flux patches" seem to be powering the anomaly's westward expansion and ongoing weakening.
“We can see one of these areas moving westward over Africa, which contributes to the weakening of the South Atlantic Anomaly in this region,” said Christopher Finlay, one of the study’s authors.
How was this detected?
Scientists made these observations using data from the European Space Agency’s Swarm mission, which relies on three identical satellites to measure magnetic signals from Earth’s interior and oceans. The mission, launched in 2013, continues to track subtle shifts in the magnetic field with remarkable precision.
Beyond the South Atlantic, the team also detected changes over Canada and Siberia. The magnetic field over Canada has weakened slightly, while the field over Siberia has strengthened. The strong magnetic zone above Canada has shrunk by an area nearly the size of India, whereas the Siberian region has expanded to an area comparable to Greenland.
Scientists think these changes are connected to the recent movement of Earth's northern magnetic pole toward Siberia, a shift that has sped up in recent decades.
What are the implications for the future?
Experts opine that further observation is crucial to find out how these changes might influence satellite operations and navigation systems. The Swarm satellites, which are in perfect shape, are likely to keep collecting data until at least 2030.
“It’s really wonderful to see the big picture of our dynamic Earth,” said Anja Strømme, ESA’s Swarm mission manager. “The satellites are all healthy and providing excellent data, so we can hopefully extend that record beyond 2030.”
While the anomaly’s growth may not immediately endanger life on Earth, its expansion is a reminder that our planet’s magnetic shield remains a dynamic and ever-changing force — one that still holds many mysteries beneath its surface.
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