What are the Van Allen belts?

The Van Allen belts (or zones) are two regions of highly charged particles above Earth’s equator trapped by the magnetic field that surrounds Earth. Also called the magnetosphere, the first belt extends from a few hundred to about 2,000 miles (3,200 kilometers) above Earth’s surface and the second is between 9,000 and 12,000 miles (14,500 to 19,000 kilometers). The particles, mainly protons and electrons, come from the solar wind and cosmic rays. The belts are named in honor of James Van Allen (1914–2006), the American physicist who discovered them in 1958 and 1959 with the aid of radiation counters carried aboard the artificial satellites Explorer I (1958) and Pioneer 3 (1959).

In May 1998 there were a series of large, solar disturbances that caused a new Van Allen belt to form in the so-called “slot region” between the inner and outer Van Allen belts. The new belt eventually disappeared once the solar activity subsided. There were also a number of satellite upsets around the same time involving the Galaxy IV satellite, Iridium satellites, and others. This is not the first time that a temporary new belt has been observed to form in the same region, but it takes a prolonged period of solar storm activity to populate this region with particles.


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