South Atlantic Anomaly
The South Atlantic Anomaly
is the region where Earth
's inner van Allen radiation belt
makes its closest approach to the planet's surface. Or, for a given altitude, the radiation intensity is higher over this region than elsewhere. It is produced by a "dip" in the Earth's magnetic field
at that location, caused by the fact that the center of Earth's magnetic field
is offset from its geographic center by 280 miles.
The South Atlantic Anomaly is of great significance to satellites and other spacecraft that orbit at several hundred miles' altitude and at orbital inclinations between 35° and 60°; these orbits take satellites through the Anomaly periodically, exposing them to several minutes of strong radiation each time. The International Space Station, orbiting with an inclination of 51.6°, required extra shielding to deal with this problem.