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1. The Van Allen Radiation Belt is a torus of energetic charged particles (plasma) around Earth, held in place by Earth’s magnetic field. The earth’s geomagnetic field is not uniformly distributed around its surface. On the sun side, it is compressed because of the solar wind and on the other side, it is elongated to around 3 earth radii. This creates a cavity called the Chapman Ferraro Cavity, in which the Van Allen radiation belts reside. The Van Allen belts are closely related to the polar aurora where particles strike the upper atmosphere and fluoresce.

   The possibility of trapped charged particles had previously been investigated by Kristian Birkeland, Carl Størmer, and Nicholas Christofilos prior to the Space Age. The existence of the belt was confirmed by the Explorer 1 on January 31, 1958, and Explorer 3 missions, under Dr. James Van Allen at the University of Iowa. The trapped radiation was first mapped out by Sputnik 3, Explorer 4, Pioneer 3 and Luna 1.

   Energetic electrons form two distinct radiation belts, while protons form a single belt. Within these belts are particles capable of penetrating about 1 g/cm2 of shielding (e.g., 1 millimetre of lead).

   The term Van Allen Belts refers specifically to the radiation belts surrounding Earth; however, similar radiation belts have been discovered around other planets. The Sun does not support long-term radiation belts. The Earth’s atmosphere limits the belts’ particles to regions above 200-1,000 km,while the belts do not extend past 7 Earth radii RE. The belts are confined to an area which extends about 65°from the celestial equator.

   An upcoming NASA mission, Radiation Belt Storm Probes will go further and gain scientific understanding (to the point of predictability) of how populations of relativistic electrons and ions in space form or change in response to changes in solar activity and the solar wind