The South Atlantic Anomaly
A large, changing area over South America and the southern Atlantic Ocean, where the Earth’s protective magnetic field is abnormally weak, is known as the South Atlantic Anomaly (SAA). NASA often likens this phenomenon to a “dent” in the magnetic field.
Consequently, the radiation shield is compromised here, allowing the inner Van Allen radiation belt to dip down to an altitude of just 200 kilometers. Therefore, high-energy protons penetrate the altitudes used by many satellites and the International Space Station (ISS).
The SAA is a scientific enigma that has been growing and weakening since its initial detection in the mid-20th century.
South Atlantic Anomaly 2025: Rapid Expansion
New data confirms the SAA is a highly dynamic and worrying feature. Measurements from the European Space Agency’s (ESA) Swarm satellite constellation show that since 2014, the unusual zone has expanded by an area around half the size of mainland Europe.
The SAA currently covers South America almost to the bottom of Africa. Moreover, the lowest intensity of the field is declining; this process has been quickening since 2020.
As a geomagnetism expert noted, the SAA is not just a single block; it’s weakening in a more intense way toward Africa compared to near South America.
Growing Risks for Satellites and Astronauts
The SAA currently poses no danger to life on Earth’s surface; however, it is of crucial importance to low-Earth-orbit satellite infrastructure. Satellites passing through the weak spot are exposed to higher doses of ionizing radiation.
Specifically, this can cause single-event upsets (SEUs), data corruption, malfunctions, or even permanent damage to electronic components. Mission teams must hence utilize ECC memory or power off sensitive equipment during SAA crossings.
Though their time in orbit is shorter than the lifespan of most satellites, astronauts are also exposed to higher dosages of radiation.
The Reasons: Supernatural Powers Deep Below the Ground
Deep within the earth, inside the outer core, where the geodynamo is driven by the churning of molten iron, the SAA’s ultimate genesis lies. Two main factors produce the South Atlantic Anomaly.
First off, the magnetic axis is slanted relative to the Earth’s axis of rotation. Secondly, a huge, dense mantle structure under Africa, known as the African Large Low Shear Velocity Province, is believed to disrupt the core flow.
Moreover, scientists observe reverse flux patches beneath the SAA, where the magnetic field, instead of coming out of the core, goes back into it. This creates a magnetic “pothole” that spacecraft feel every time they pass through.
A Moving Target: Drift and the Two-Lobe Shape
The weak zone is not static; it shows a slow northwest drift. More remarkably, since around 2020, the minimum has begun to split, forming two lobes with separate centers of lowest intensity. This splitting creates more traps for low-Earth orbiters.
Consequently, models must track the drift speed and the degree of splitting to refine risk maps. Scientists stress that while the SAA is part of the Earth’s secular variation, and similar weak patches are seen in the geological past, there is nothing for people to be alarmed about regarding an imminent pole reversal.
Other Global Magnetic Shifts
The Swarm data also reveals other global shifts. A strong magnetic field region over Siberia has grown in size, while a strong region over Canada has shrunk. These unexpected changes are related to core circulation patterns and are associated with the northern magnetic pole moving toward Siberia.
South Atlantic Anomaly Climate Change Context
There is very little relationship between the South Atlantic Anomaly and Climate Change. Although the SAA impacts technology and space weather, the Earth’s heavy atmosphere keeps the charged particles from reaching the surface; therefore, the phenomenon does not directly affect the climate or weather patterns of our planet.
Conclusion
The southern Atlantic, one of the most important issues in geophysics and space safety, is an anomaly. The ongoing satellite observation of Swarm offers important information about the dynamics of the deep Earth and the growing dangers to our orbital network.
Consequently, mission planners have to keep their operational playbooks current so they may negotiate this increasing magnetic weak spot.
