The South Atlantic Anomaly (SAA) is an area where the Earth's inner Van Allen radiation belt comes closest to the Earth's surface, dipping down to an altitude of 200 kilometres (120 mi). This leads to an increased flux of energetic particles in this region and exposes orbiting satellites to higher-than-usual levels of radiation. The effect is caused by the non-concentricity of the Earth and its magnetic dipole. The SAA is the near-Earth region where the Earth's magnetic field is weakest relative to an idealized Earth-centered dipole field. The area of the SAA is confined by the intensity of Earth's magnetic field at less than 32,000 nanotesla at sea level, which corresponds to the dipolar magnetic field at ionospheric altitudes. However, the field itself varies in intensity as a gradient. Read more

Marker for the collapse of key Atlantic current discovered   Live Science - February 9, 2024

A vital Atlantic current that includes the Gulf Stream and keeps our climate in check may be giving off a warning sign of collapse.

Ocean system that moves heat gets closer to collapse, which could cause weather chaos, study says   PhysOrg - February 9, 2024

Marker for the collapse of key Atlantic current discovered   Live Science - February 9, 2024

A vital Atlantic current that includes the Gulf Stream and keeps our climate in check may be giving off a warning sign of collapse.

NASA is actively monitoring a strange anomaly in Earth's magnetic field: a giant region of lower magnetic intensity in the skies above the planet, stretching out between South America and southwest Africa   Science Alert - March 23, 2023

This vast, developing phenomenon, called the South Atlantic Anomaly, has intrigued and concerned scientists for years, and perhaps none more so than NASA researchers. The space agency's satellites and spacecraft are particularly vulnerable to the weakened magnetic field strength within the anomaly, and the resulting exposure to charged particles from the Sun. The South Atlantic Anomaly (SAA) - likened by NASA to a 'dent' in Earth's magnetic field, or a kind of 'pothole in space' - generally doesn't affect life on Earth, but the same can't be said for orbital spacecraft (including the International Space Station), which pass directly through the anomaly as they loop around the planet at low-Earth orbit altitudes.

NASA researchers track slowly splitting 'dent' in Earth's magnetic field   PhysOrg - August 17, 2020

A small but evolving dent in Earth's magnetic field can cause big headaches for satellites. Earth's magnetic field acts like a protective shield around the planet, repelling and trapping charged particles from the Sun. But over South America and the southern Atlantic Ocean, an unusually weak spot in the field - called the South Atlantic Anomaly, or SAA - allows these particles to dip closer to the surface than normal. Particle radiation in this region can knock out onboard computers and interfere with the data collection of satellites that pass through it - a key reason why NASA scientists want to track and study the anomaly.

The South Atlantic Anomaly May Go Back Far Longer Than Anybody Knew   Science Alert - July 22, 2020

For years, scientists have been gripped by the existence of a strange anomaly weakening Earth's magnetic field. It's located in the midst of the South Atlantic ocean, extending all the way from South America to the west coast of southern Africa. This giant, puzzling expanse of reduced magnetic intensity – which in recent times looks to be splitting into two divided entities - means the region offers less protection against harmful radiation from the Sun for Earth's satellites.

That's a problem for spacecraft today. But perhaps the greatest significance of the 'South Atlantic Anomaly' is what it might mean for tomorrow: specifically, whether the mysterious phenomenon foreshadows the beginnings of a complete polar reversal of Earth's magnetic field. Such giant magnetic flips have occurred many times in our planet's history, and some scientists have speculated that the South Atlantic Anomaly could be a kind of precursor to these rare global transitions.