Earth’s Magnetic Field Shows Intensifying Weakness in South Atlantic Anomaly
Recent data from ESA’s Swarm satellite constellation reveals a important expansion of the South Atlantic Anomaly (SAA), a region where Earth’s magnetic field is unusually weak, since 2014. A study published in Physics of the Earth and Planetary Interiors links this development to unusual activity at the boundary between Earth’s liquid outer core and its rocky mantle.
The SAA was first identified in the late 1950s with the advent of satellite-based magnetic field measurements. Satellites passing through this area experience elevated levels of radiation, posing a challenge to the safety and operation of space missions.
According to Chris Finlay, professor of geomagnetism at the Technical University of Denmark and lead author of the study, the SAA isn’t a uniform weakness. “There’s something special happening in this region that is causing the field to weaken in a more intense way,” he stated. Specifically, Swarm data indicates that, unlike typical magnetic field patterns where lines emerge from the core in the southern hemisphere, the SAA exhibits areas where the magnetic field re-enters the core. One such area is currently moving westward over Africa, contributing to the anomaly’s growth.
While the SAA is intensifying, changes are also occurring in areas of magnetic field strength. A strong region over Canada has weakened, shrinking by 0.65% of Earth’s surface area – an area nearly the size of India. Conversely, a strong region over Siberia has grown by 0.42%, roughly the size of Greenland.
Earth’s magnetic field is vital for life, shielding the planet from harmful cosmic radiation and solar wind, and protecting the atmosphere. The Swarm mission, launched in 2013, utilizes three satellites – Alpha, Bravo, and Charlie – to map the complex structure of the magnetic field, originating from the core, crust, oceans, and atmosphere, and track its dynamic changes.Finlay emphasizes that understanding Earth’s magnetic field requires recognizing its complexity,stating,”It’s only by having satellites like Swarm that we can fully map this structure and see it changing.”
