Van Al'len belt"
either of two regions of high-energy-charged particles surrounding the earth, the inner region centered at an altitude of 2000 mi. (3200 km) and the outer region at an altitude between 9000 and 12,000 mi. (14,500 and 19,000 km). Also called Van Al'len radia'tion belt".
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.