A region of the Earth centered near 25S and 50W (near the Atlantic coast of Brazil) of low geomagnetic field intensity owing to the fact that the geomagnetic field axis is offset from the center of th
e Earth. One consequence of the SAA is that trapped particles in the plasmasphere drift closer to the Earth’s surface and can more easily be lost into the atmosphere. The result is that the F region (see ionosphere) is highly variable in this region, and satellites in low Earth orbits suffer greater radiation doses when they pass through the SAA. There is a corresponding location of maximum geomagnetic field intensity in Southeast Asia.
The region where the Earth's inner van Allenradiation belt makes its closest approach to the planet's surface. Theresult is that, for a given altitude, the radiation intensity is higher overthis regio
n than elsewhere.
The point in the southern hemisphere where the rotation axis of the Earth touches the celestial sphere. In contrast to the north celestial pole, no bright star is visible in that direction.