Van Allen radiation belts
The region of the radiation belts has been given the name of magnetosphere to distinguish it from the atmosphere. The high-energy particles of which the belts are composed circulate along the earth's magnetic lines of force extending from the area above the equator to near (but not above) the North and South Poles. The inner belt is mainly protons with some electrons; the outer one mainly electrons. The particles of the inner belt are believed to be produced by the collisions of cosmic rays with atoms in the upper atmosphere. Those of the outer belt are believed to originate both from the atmosphere and from the solar wind; particles from the solar wind become trapped by the earth's magnetic field and are responsible for the aurora borealis seen at polar regions. A part of a belt dips into the upper region of the atmosphere over the South Atlantic to form the Southern Atlantic Anomaly. This can present a dangerous hazard to satellites orbiting the earth.
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.
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