- a broad, doughnut-shaped region surrounding the earth and composed of high-energy electrons and protons trapped in the earth's magnetic field at heights between c. 400 km (c. 250 mi) and c. 64,370 km (c. 40,000 mi)
- such a region surrounding other planets, as Jupiter
Origin:
after James A. Van Allen (1914-2006), U.S. physicist