From Wikipedia
The South Atlantic Anomaly (or SAA) is the region where Earth’s inner Van Allen radiation belt makes its closest approach to the planet’s surface. For a given altitude, the radiation intensity is greater within this region than elsewhere.The Van Allen radiation belts are symmetric with the Earth’s magnetic axis, which is tilted with respect to the Earth’s rotational axis by an angle of ~11 degrees. Because of this tilt, the inner Van Allen belt is closest to the Earth’s surface over the south Atlantic ocean, and farthest from the Earth’s surface over the north Pacific ocean.
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