South Atlantic Anomaly

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 200km (124mi). 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, and the SAA is the near-Earth region where the Earth's magnetic field is weakest.