A colossal weak spot in Earth's protective magnetic field has expanded dramatically over the past decade, growing by an area nearly half the size of Europe, according to a new scientific study.
What is the South Atlantic Anomaly?
Discovered in 1958, the South Atlantic Anomaly represents a significant dip in our planet's magnetic shield. This region stretches from South America across the southern Atlantic Ocean toward southwestern Africa, covering approximately 4.3 million square miles.
Professor Chris Finlay, the study's lead author from the Technical University of Denmark, explains that the magnetic strength in this area is unusually weak. 'By "unusually weak" we mean the strength in this region is only about half what would be expected if it were a simple tilted dipole,' he told Metro.
Think of Earth's magnetic field like a dynamo bike lamp, where light is generated by pedalling. Instead of a cyclist's feet, it's an ocean of molten iron 1,900 miles beneath the surface that creates this protective field. Normally, this field extends about 400 miles high, but over the South Atlantic, it only reaches approximately 120 miles high.
Why is the Magnetic Field Hole Growing?
The research, published in the journal Physics of the Earth and Planetary Interiors, analysed 11 years of measurements from the European Space Agency's Swarm mission satellites, launched in 2013.
Anja Strømme, the Swarm mission manager, revealed the anomaly is caused by peculiar behaviour in Earth's liquid core and rocky mantle. 'Beneath the South Atlantic Anomaly, the magnetic field lines are going in the "wrong" direction, they are going into the core instead of coming out,' she explained.
These reversed magnetic flux regions have separated under South America and southern Africa, causing the overall anomaly to expand. Since 2014, the weak spot has grown by about two million square miles and changed shape, developing a lobe towards Africa where the field is weakening rapidly.
Should We Be Concerned About This Expansion?
The immediate concern involves satellites and technology. Richard Holme, Professor of Geophysics at the University of Liverpool, notes that cosmic rays penetrating this weak spot can short-circuit satellites or cause electrical surges leading to blackouts.
'Astrophysics satellites are routinely switched off when they fly over that area,' Holme said. 'For Earth observing satellites, this is more difficult – if you want to look at the Amazon, then turning off every time you fly over it doesn't work!'
Some scientists have suggested this weakening might indicate the beginning of a magnetic pole reversal, where Earth's north and south poles flip. However, Professor Holme offers reassurance: 'This has happened many times in Earth's history, and it hasn't been shown to be associated with anything particularly nasty like a mass extinction.'
He adds that while the field is weakening, evidence suggests it's not actually reversing at the moment and will likely recover its strength. The changes observed also include the magnetic field shrinking over Canada by about India's size while swelling over Siberia by Greenland's area, likely due to Earth's north pole shifting toward Siberia.
Professor Finlay emphasises that despite appearances, scientists still have much to learn about Earth's magnetic field. 'We are working to better understand this process, but don't yet know all the details,' he concluded.
