NASA is closely monitoring the South Atlantic Anomaly (SAA), a growing region of weakened magnetic field between South America and southwest Africa that has expanded since 2014 by roughly half the size of continental Europe. The SAA exposes low-Earth-orbit satellites and the ISS to higher fluxes of solar charged particles, increasing the risk of glitches, data loss, or hardware damage. Scientists link the anomaly to disturbances in core-generated magnetic fields—including influence from a deep dense reservoir beneath Africa—and observations show the feature is drifting and may be splitting into two centers. Continued satellite missions such as ESA's Swarm and CubeSat tracking are essential to improve models, predict changes, and protect space assets.
NASA Tracks an Expanding 'Dent' in Earth's Magnetic Shield — Inside the South Atlantic Anomaly
NASA is closely monitoring the South Atlantic Anomaly (SAA), a growing region of weakened magnetic field between South America and southwest Africa that has expanded since 2014 by roughly half the size of continental Europe. The SAA exposes low-Earth-orbit satellites and the ISS to higher fluxes of solar charged particles, increasing the risk of glitches, data loss, or hardware damage. Scientists link the anomaly to disturbances in core-generated magnetic fields—including influence from a deep dense reservoir beneath Africa—and observations show the feature is drifting and may be splitting into two centers. Continued satellite missions such as ESA's Swarm and CubeSat tracking are essential to improve models, predict changes, and protect space assets.
NASA monitors a growing weak zone in Earth’s magnetic shield
NASA has long tracked an unusual, large region of weakened magnetic intensity above the South Atlantic, stretching between South America and southwest Africa. Known as the South Atlantic Anomaly (SAA), this area forms a pronounced dip in Earth's protective magnetic field and has grown substantially in recent years.
Recent measurements indicate the anomaly has expanded since 2014 by an area roughly equivalent to half the size of continental Europe, while the field strength within the zone continues to decline. Although the SAA rarely affects life on the planet's surface, it is a serious concern for satellites and spacecraft in low-Earth orbit, including the International Space Station. The weaker field inside the anomaly allows higher fluxes of charged solar particles to reach spacecraft systems, increasing the likelihood of transient glitches, data loss, or even permanent hardware damage.
To reduce risk, operators sometimes power down or reconfigure sensitive systems before their spacecraft pass through the anomaly. Tracking and studying the SAA helps mission teams mitigate those operational hazards, and it also offers an exceptional scientific laboratory for probing complex processes in Earth's deep interior.
'The magnetic field is actually a superposition of fields from many current sources,' explained NASA Goddard geophysicist Terry Sabaka in 2020. The dominant component originates from flows of molten iron in Earth's outer core, but local perturbations can create notable regional weaknesses.
One leading explanation links the SAA to disturbances in core dynamics caused by a dense structure beneath Africa called the African Large Low Shear Velocity Province (LLSVP), located about 2,900 km beneath the continent. That deep anomaly, together with the tilt and complex geometry of Earth's magnetic field, appears to foster a localized, weakened region above the South Atlantic.
NASA researchers and international teams have uncovered additional behavior: a 2016 study led by NASA heliophysicist Ashley Greeley showed the SAA drifts slowly over time, and CubeSat tracking confirmed that motion in 2021. In 2020 researchers reported the SAA may be splitting into two distinct centers of minimum intensity, a morphological change whose long-term consequences remain uncertain. A July 2020 paper suggests similar anomalies have recurred intermittently for millions of years, possibly as far back as 11 million years, implying the SAA may be a recurrent feature rather than an immediate precursor of a global geomagnetic reversal.
Newer results continue to add nuance. A 2024 study connected the SAA with alterations in auroral behavior, and ESA's Swarm satellite trio has revealed that the weakening is evolving differently toward Africa than over South America. As Chris Finlay of the Technical University of Denmark observed, 'There's something special happening in this region that is causing the field to weaken in a more intense way.'
Despite remaining uncertainties, sustained observation is essential. Continued satellite missions and ground-based studies let scientists refine models, forecast changes, and advise satellite operators about mitigation strategies. The SAA is an evolving, slow-moving feature — not an immediate threat to life on Earth — but it is a practical concern for the space infrastructure that modern society depends on.
Key takeaways:
- The South Atlantic Anomaly is a large region of weaker magnetic intensity above the South Atlantic that has expanded since 2014.
- It increases exposure of low-Earth-orbit spacecraft to charged particles, raising the risk of glitches and hardware damage.
- Deep Earth structures such as the African LLSVP likely perturb core flows and contribute to the anomaly.
- Observations show the SAA drifts, may be splitting into two cells, and has possibly recurred over millions of years; continued monitoring by missions like ESA's Swarm and CubeSat campaigns is critical.