A major dip in the Earth’s magnetic field over the South Atlantic has been puzzling scientists for over a century.
Perhaps most strangely, the weak spot — dubbed the South Atlantic Anomaly — has grown rapidly over the last eleven years. That’s according to satellite data suggests showing it’s expanded by an area equivalent to half the size of continental Europe, as detailed in a new paper published in the journal Physics of the Earth and Planetary Interiors.
An international team of researchers analyzed data collected by the European Space Agency’s Swarm, a constellation comprised of three identical satellites that measure the Earth’s magnetic signals.
The findings could allow us to improve existing magnetic models that play a crucial role in navigation and tracking of space weather, while also furthering our understanding of how the Earth’s layers interact with each other.
Scientists’ best theory is that an enormous, swirling body of molten iron in the planet’s outer core — roughly 1,800 miles below the surface — could be generating the major dip in the magnetic field.
But that’s only one of many factors influencing this weakening, with scientists working to identify the other factors at play. As detailed in this latest paper, the spot is behaving in all kinds of unexpected ways as it continues to expand rapidly.
“The South Atlantic Anomaly is not just a single block,” said lead author and Technical University of Denmark professor of geomagnetism Chris Finlay in a statement. “It’s changing differently towards Africa than it is near South America. There’s something special happening in this region that is causing the field to weaken in a more intense way.”
“Normally we’d expect to see magnetic field lines coming out of the core in the southern hemisphere,” Finlay explained. “But beneath the South Atlantic Anomaly we see unexpected areas where the magnetic field, instead of coming out of the core, goes back into the core.”
Besides the anomaly, Swarm data has also found that the magnetic field is strengthening over Siberia, while weakening over Canada.
Scientists believe the complex processes behind the shifts are linked to the northern magnetic pole wandering towards Siberia over the last few years.
“When you’re trying to understand Earth’s magnetic field, it’s important to remember that it’s not just a simple dipole, like a bar magnet,” said Finlay. “It’s only by having satellites like Swarm that we can fully map this structure and see it changing.”
The ESA is expected to extend its Swarm mission beyond 2030, which could allow researchers to continue tracking the odd behavior of our planet’s magnetic field for many years to come.
More on the Earth’s magnetic field: Scientists Say They Detected Something Huge Shifting Inside the Earth