Van Allen radiation belts are zones of high-energy particles (especially protons) trapped by the earth’s magnetic field. Most of these high-energy particles originate from the solar wind captured by and held around a planet by that earth’s magnetic field. The van Allen belt is formed like a torus above the equator. There are two van Allen radiation belts, an internal belt is centered at about 3,000 kilometers, and an outer belt is centered at about 22,000 kilometers from the earth’s surface. It contains mainly energetic protons in the 10-100 MeV range.
Spacecraft traveling beyond low Earth orbit enter the zone of radiation of the Van Allen belts. Beyond the belts, they face additional hazards from cosmic rays and solar particle events. A region between the inner and outer Van Allen belts lies at two to four Earth radii and is sometimes referred to as the “safe zone.”