Regions of the magnetosphere roughly 1.2 to 6 earth radii above the equator in which charged particles are stably trapped by closed geomagnetic field lines. There are two belts. The inner belt is part of the plasmasphere and corotates with earth. The outer belt extends on to the magnetopause on the sunward side (10 earth radii under normal quiet conditions) and to about 6 earth radii on the nightside. The radiation belts are often called the "Van Allen radiation belt" because the were discovered in 1968 by J.A. Van Allen.