A significant drop in the Earth’s magnetic field over the South Atlantic has intrigued scientists for more than a century.
Perhaps strangest of all, the weak spot – dubbed the South Atlantic Anomaly – has grown rapidly over the past eleven years. That’s suggested by satellite data showing it has expanded by an area equivalent to half the size of continental Europe, as detailed in a new paper published in the journal. Earth physics and planetary interiors.
An international team of researchers analyzed data collected by the European Space Agency’s Swarm, a constellation made up of three identical satellites that measure Earth’s magnetic signals.
The results could allow us to improve existing magnetic models that play a crucial role in navigation and tracking space weather, while deepening our understanding of how Earth’s layers interact with each other.
Scientists’ best theory is that a huge swirling body of molten iron in the planet’s outer core — about 1,800 miles below the surface — could generate a major drop in the magnetic field.
But that’s just one of many factors influencing this weakening, as scientists work to identify what other factors are at play. As detailed in this latest article, the spot behaves in all kinds of unexpected ways as it continues to rapidly expand.
“The South Atlantic anomaly is not just one block,” Chris Finlay, lead author and 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.”
“Normally, we would expect to see magnetic field lines coming out of the core of the southern hemisphere,” Finlay explained. “But beneath the South Atlantic anomaly, we see unexpected areas where the magnetic field, instead of leaving the core, returns to it.”
In addition to this anomaly, the Swarm data also revealed that the magnetic field strengthens over Siberia, while weakening over Canada.
Scientists believe that the complex processes behind these changes are linked to the wandering of the north magnetic pole towards Siberia in recent years.
“When you’re trying to understand the Earth’s magnetic field, it’s important to remember that it’s not a simple dipole, like a bar magnet,” Finlay said. “Only by having satellites like Swarm can we fully map this structure and see how it evolves.”
The ESA is expected to extend its Swarm mission beyond 2030, which could allow researchers to continue tracking the strange behavior of our planet’s magnetic field for many years to come.
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