The South Atlantic Anomaly expands and weakens the Earth's magnetic field.

The weakest region of the planet's geomagnetic shield, the so-called South Atlantic Anomaly, continues to change: new models developed with satellite data indicate a sustained expansion and progressive weakening. In this context, ESA confirms that the fragile area has expanded since 2014 and that its behavior is not uniform throughout the South Atlantic.

Tracking with the Swarm constellation—three identical satellites launched in 2013—offers the longest and most accurate orbital record of the Earth's magnetic field. According to this analysis, The anomaly now covers an area equivalent to almost half of Europe and the deterioration is especially pronounced near the end facing Africa since around 2020.

What is the South Atlantic Anomaly and why does it matter?

The South Atlantic Anomaly (SAA) is a vast area between South America and southern Africa where the intensity of the Earth's magnetic field is unusually lowThis weakness allows more energetic particles to penetrate at lower altitudes, increasing the radiation dose received by satellites and, to a lesser extent, astronauts when they cross the region.

In practical terms, passing through AAS increases the risk of electronic component failures, spontaneous reboots, and memory errors in ships and sensors, in addition to affect navigation and positioning instruments such as GPS. Therefore, the area is a priority checkpoint for space mission operators and insurers.

Measurements from space: eleven years of Swarm data

The new study, led by Chris Finlay (Technical University of Denmark) and published in the journal Physics of the Earth and Planetary Interiors, is based on eleven years of detailed measurements of the magnetic field carried out by the European Space Agency's Swarm mission (ESA).

The resulting maps show that the AAS has spread eastward since 2014 and its evolution is not homogeneous: near South America the changes are milder, while off the southwest coast of Africa the weakening has clearly accelerated since 2020.

Uneven weakening and patches of reverse flow

To explain this pattern, researchers point to dynamics at the boundary between the liquid outer core and the rocky mantle. There, reverse flow “patches” which alter the usual direction of the field lines; instead of exiting into space in the southern hemisphere, part of the flow is directed back toward the core.

Swarm data indicate that one of those patches is moving westward under Africa, contributing to local loss of intensity as the AAS gains ground in that sector. In addition, a secondary minimum is outlined southwest of the African continent, a sign that the anomaly could fragment into magnetic “cells” with somewhat different behaviors.

Impact on satellites, navigation and space risk management

A wider and weaker AAS complicates the planning of orbits, observation windows and hardware protection protocolsSatellite operators incorporate maneuvers, preventive shutdowns or redundancies when they cross the region, with the aim of in order to reduce the likelihood of breakdowns and extend the useful life of your equipment.

These Precautions make even more sense during periods of maximum solar activity., when the solar wind and coronal mass ejections increase the flux of charged particles. Space weather prediction and navigation models require frequent updates to reflect the variations detected by Swarm.

A moving magnetic field on a global scale

Beyond the South Atlantic, the dataset reveals opposite trends in other regions: the field over Siberia has been reinforced While a historically intense zone over Canada has lost area. These changes are related to the shift of the magnetic north pole toward Siberia observed in recent decades.

The Swarm time series—which ESA aims to extend beyond 2030—allows detailed monitoring of magnetic pole drift and quickly adjust reference geomagnetic models used by navigation, mapping and geophysical exploration systems.

What to expect from now on

Scientists emphasize that the observed oscillations are part of the dynamic nature of the Earth's geodynamo and do not imply an imminent pole shift. Still, continued monitoring is crucial to understanding the evolution of AAS and mitigating its technological impact with improved designs, shielding, and operational strategies.

With what has been observed so far, The South Atlantic Anomaly continues to expand and become more intense, especially towards Africa, in a context of global variations in the magnetic field. Swarm monitoring provides the basis for Anticipate risks, update models, and keep systems safe that depend on the invisible shield that surrounds our planet.