Van Allen radiation belts Two rings of radiation trapped by the Earth's magnetic field in the upper atmosphere. The belts contain high-energy, charged particles. The inner belt (of electrons and protons) extends from c.1000 to 4000km (600–2500mi) above the Equator. The outer belt (of electrons) extends from c.15,000 to 25,000km (9000–15,000mi). It is thought that the particles come from solar flares carried by the solar wind. The belts were discovered in 1958 by the US physicist James Van Allen.

Van Allen belt Two belts of high-energy, charged particles trapped by the Earth's magnetic field within the magnetosphere. The inner belt starts at an altitude of about 800 km and reaches a maximum intensity at about 2000 km. The outer belt reaches a maximum intensity at between three and four Earth radii (18 000–25 000 km). Although commonly referred to as ‘radiation belts’, they contain particles, not radiation. Their presence was predicted by J. A. Van Allen (1914– ).

Van Al·len belt • n. each of two regions of intense radiation partly surrounding the earth at heights of several thousand kilometers.