The South Atlantic Anomaly (SAA), a weakening region in Earth’s magnetic field, has expanded significantly since 2014, according to an 11-year analysis of ESA’s Swarm satellite data. The study links the anomaly to unusual behaviour at the core–mantle boundary and a westward drift across Africa. Changes in northern magnetic patches (strengthening over Siberia and weakening over Canada) also alter satellite radiation exposure and navigation accuracy. Operators warn the SAA may raise radiation risk for low Earth orbit spacecraft and crewed missions.
Earth’s Magnetic “Weak Spot” Has Grown — Could Raise Radiation Risk for Satellites
The South Atlantic Anomaly (SAA), a weakening region in Earth’s magnetic field, has expanded significantly since 2014, according to an 11-year analysis of ESA’s Swarm satellite data. The study links the anomaly to unusual behaviour at the core–mantle boundary and a westward drift across Africa. Changes in northern magnetic patches (strengthening over Siberia and weakening over Canada) also alter satellite radiation exposure and navigation accuracy. Operators warn the SAA may raise radiation risk for low Earth orbit spacecraft and crewed missions.
09:55 PM, 11/12/2025Science
Growing South Atlantic Anomaly could increase satellite radiation exposure
A widening weak patch in Earth’s magnetic field — the South Atlantic Anomaly (SAA) — has expanded markedly since 2014 and may increase radiation risks for satellites and crewed spacecraft, according to a new analysis of satellite data.
The geomagnetic field, which protects life by deflecting charged particles from the Sun and cosmic radiation, is generated by complex flows of molten iron in Earth’s outer core about 3,000 km beneath the surface. Although the basic dynamo mechanism is understood, the detailed behaviour of the field is highly variable and not yet fully explained.
Researchers used data from the European Space Agency’s Swarm satellite constellation — three identical satellites launched in 2013 that separate magnetic signals from the core, mantle, crust, oceans and upper atmosphere — to track 11 years of changes. The study, published in Physics of the Earth and Planetary Interiors, finds the SAA has enlarged by an area roughly nearly half the size of continental Europe since 2014.
Scientists link the anomaly’s distortion to unusual behaviour at the boundary between the liquid outer core and the solid mantle. Normally magnetic field lines emerge from the core in the southern hemisphere, but beneath parts of the SAA the lines instead dive back into the core — an unexpected configuration that weakens the field at satellite altitudes.
“The South Atlantic Anomaly is not a single, solid feature. It is evolving differently toward Africa than it is near South America. Something unusual is occurring in this region that is intensifying the field’s weakening,” says Chris Finlay, lead author and scientist at the Technical University of Denmark.
Swarm observations show one weakened region drifting westward across Africa, contributing to the anomaly’s changing shape. At the same time, the field has strengthened over Siberia and weakened over Canada — a shifting balance that influences navigation systems and the radiation dose encountered by low Earth orbit satellites.
Researchers warn that spacecraft and crewed platforms, including the International Space Station, passing through the SAA may face elevated radiation levels, increasing the risk of electronic faults, data corruption and operational disruptions. Operators can mitigate some risks with shielding, fault-tolerant design and careful mission planning, but a changing geomagnetic environment adds complexity to satellite operations.
What this means: the SAA’s growth is a measurable, evolving feature of Earth’s magnetic field that has practical implications for satellite reliability, astronaut safety and navigation systems that depend on magnetic models.