The South Atlantic Magnetic Anomaly (SAMA) refers to the area where the Earth's inner Van Allen radiation belt comes closest to the Earth's surface. 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. The SAMA is the near-Earth region where the Earth´s magnetic field is weakest.
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. The intersection between the magnetic and rotation axis of the Earth is located ~500 kilometers (300miles) more to the North, above the centre of the Earth. Because of this tilt and translation, 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
The illustration shows a cross-sectional view of the Van Allen radiation belts, noting the point where the South Atlantic Anomaly occurs
The South Atlantic Magnetic Anomaly is of great significance to astronomical satellites and other spacecraft that orbit the Earth at several hundred kilometers altitude; these orbits take satellites through the anomaly periodically, exposing them to several minutes of strong radiation, caused by the trapped protons in the inner Van Allen belt, each time. The International Space Station, orbiting with an inclination of 51.6°, requires extra shielding to deal with this problem. The Hubble Telescope does not take observations while passing through the SAMA. Astronauts are also affected by this region which is said to be the cause of peculiar 'shooting stars' seen in the visual field of astronauts.
The shape of the SAMA changes over time. Since its initial discovery in 1958, the southern limits of the SAMA have remained roughly constant while a long-term expansion has been measured to the northwest, the north, the northeast, and the east. Additionally, the shape and particle density of the SAMA varies on a diurnal basis, with greatest particle density corresponding roughly to local noon. At an altitude of approximately 500 km (300 mi), the SAMA spans from -50° to 0° geographic latitude and from -90° to +40° longitude. The highest intensity portion of the SAMA drifts to the west at a speed of about 0.3 degrees per year. The drift rate of the SAA is very close to the rotation differential between the Earth´s core and its surface, estimated to be between 0.3 and 0.5 degrees per year.
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. The intersection between the magnetic and rotation axis of the Earth is located ~500 kilometers (300miles) more to the North, above the centre of the Earth. Because of this tilt and translation, 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
The illustration shows a cross-sectional view of the Van Allen radiation belts, noting the point where the South Atlantic Anomaly occurs
The South Atlantic Magnetic Anomaly is of great significance to astronomical satellites and other spacecraft that orbit the Earth at several hundred kilometers altitude; these orbits take satellites through the anomaly periodically, exposing them to several minutes of strong radiation, caused by the trapped protons in the inner Van Allen belt, each time. The International Space Station, orbiting with an inclination of 51.6°, requires extra shielding to deal with this problem. The Hubble Telescope does not take observations while passing through the SAMA. Astronauts are also affected by this region which is said to be the cause of peculiar 'shooting stars' seen in the visual field of astronauts.
The shape of the SAMA changes over time. Since its initial discovery in 1958, the southern limits of the SAMA have remained roughly constant while a long-term expansion has been measured to the northwest, the north, the northeast, and the east. Additionally, the shape and particle density of the SAMA varies on a diurnal basis, with greatest particle density corresponding roughly to local noon. At an altitude of approximately 500 km (300 mi), the SAMA spans from -50° to 0° geographic latitude and from -90° to +40° longitude. The highest intensity portion of the SAMA drifts to the west at a speed of about 0.3 degrees per year. The drift rate of the SAA is very close to the rotation differential between the Earth´s core and its surface, estimated to be between 0.3 and 0.5 degrees per year.
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