South Atlantic Anomaly

26°37′S 49°04′W / 26.61°S 49.06°W / -26.61; -49.06

The strength of Earth's magnetic field, as of 2020 (10−9 T)

The South Atlantic Anomaly (SAA) is an area where Earth's inner Van Allen radiation belt comes closest to 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 (including the ISS) to higher-than-usual levels of ionizing radiation.

The effect is caused by the non-concentricity of Earth with its magnetic dipole and has been observed to be increasing in intensity recently.[quantify] The SAA is the near-Earth region where Earth's magnetic field is weakest relative to an idealized Earth-centered dipole field.