Earth’s magnetic field has a weak spot called the South Atlantic Anomaly (SAA). This region has been expanding rapidly, growing over an area almost as large as Europe in just 11 years. Data from the European Space Agency’s Swarm satellites shows that the SAA has changed a lot since 2014. A recent study in *Physics of the Earth and Planetary Interiors* links this growth to unusual patterns at the boundary between Earth’s liquid outer core and its solid inner core.
Chris Finlay, a geomagnetism expert from the Technical University of Denmark and lead author of the study, noted, “The South Atlantic Anomaly isn’t a single block. There’s something special happening in this area, causing the field to weaken intensely.”
Why is this weak spot important? The magnetic field is crucial for our planet. It shields us from cosmic radiation and solar winds, which helps maintain our atmosphere and protects vital resources, like water.
The SAA was first discovered in the late 1950s when early satellites began measuring the magnetic field. Scientists noticed higher radiation levels in this particular area, indicating a weaker magnetic field compared to others.
Satellites flying over the SAA pick up higher radiation doses, which raises safety concerns for space missions. Finlay explained, “We expect magnetic field lines to emerge from the core in the southern hemisphere. But in the SAA, they often go back into the core.”
The Swarm data also shows that one area of the anomaly is shifting westward over Africa, contributing to its weakening. Interestingly, two strong points in the northern hemisphere—one near Canada and the other in Siberia—have shown different trends. The Canadian strong spot has shrunk by about 0.65% of Earth’s surface area, roughly the size of India, while the Siberian area has grown by 0.42%, comparable to Greenland.
Finlay emphasizes the complexity of the magnetic field, stating, “It’s not just a simple dipole like a bar magnet. Satellites like Swarm are crucial for mapping these changes.” ESA’s Swarm mission, launched in 2013, uses three satellites—Alpha, Bravo, and Charlie—to gather data about magnetic signals from Earth’s core, crust, oceans, and atmosphere.
Recent analyses show that the SAA’s expansion could have lasting effects on our technology and environment. While the reasons for its growth are still being explored, this phenomenon shows how dynamic and changing Earth’s magnetic field can be—a reminder of our planet’s complexity.
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