The Growing South Atlantic Anomaly: Insights from Satellite Data

Recent findings from the European Space Agency (ESA) reveal a significant development in the Earth’s magnetic field, particularly concerning a weak spot over the South Atlantic Ocean. This anomaly, known as the South Atlantic Anomaly (SAA), has been under observation for over a decade, with satellite data indicating a notable expansion and increasing intensity of its weakening.

The Earth’s magnetic field serves as a protective shield against cosmic radiation and solar particles, generated by the dynamic movements of molten iron in the planet’s outer core. The SAA was first identified in the 19th century and is located southeast of South America and southwest of Africa. In this region, the magnetic field dips, exposing satellites that traverse it to higher levels of radiation, which can lead to technical malfunctions and even blackouts.

From 2014 to 2025, the ESA conducted an extensive study using three satellites known as Swarm, which meticulously measured the planet’s magnetic signals. The findings were published in the journal Science Direct, revealing that the SAA has expanded by nearly two million square miles—an area almost half the size of continental Europe. Notably, the rate of weakening has accelerated since 2020, with variations in the anomaly’s behavior observed in different locations.

Chris Finlay, a Professor of Geomagnetism at the Technical University of Denmark and lead author of the study, emphasized that the SAA is not uniform. “It’s changing differently towards Africa than it is near South America,” he stated. This suggests that unique geological processes are at play in this region, contributing to the intensified weakening of the magnetic field.

One intriguing aspect of the study is the observation that magnetic field lines from the Earth’s core appear to be bouncing back into it, a phenomenon that remains poorly understood but is believed to exacerbate the SAA’s weakening in specific areas.

Beyond the SAA, the ESA’s satellites have identified other anomalies in the Earth’s magnetic field. In the southern hemisphere, a region of particularly strong magnetic activity exists, while two notable anomalies in the northern hemisphere—one near Canada and the other over Siberia—exhibit contrasting behaviors. The anomaly near Canada has shrunk significantly, while the one over Siberia has expanded, mirroring the dynamic nature of Earth’s magnetic field.

Looking ahead, the ESA plans to continue monitoring the magnetic field through the Swarm satellites, which are currently providing valuable data. Anja Stromme, the Swarm Mission manager, expressed optimism about the future of this research, stating, “The satellites are all healthy and providing excellent data, so we can hopefully extend that record beyond 2030, when the solar minimum will allow more unprecedented insights into our planet.”

As scientists delve deeper into the complexities of the Earth’s magnetic field, the implications of these findings extend beyond academic interest. Understanding the dynamics of the South Atlantic Anomaly and its counterparts can enhance our knowledge of Earth’s geophysical processes and their potential impacts on technology and life on our planet.