from The American Heritage® Dictionary of the English Language, 4th Edition
- n. Either of two zones of high-intensity particulate radiation trapped in Earth's magnetic field and surrounding the planet, beginning at an altitude of about 800 kilometers (500 miles) and extending tens of thousands of kilometers into space.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. Either of two torus-shaped areas of high-energy charged particles which partly surround Earth, trapped by its magnetic field. The areas are characterised by intense radiation. When the belts "overload", particles strike the upper atmosphere and fluoresce, causing the polar aurora.
- n. Any of similar areas around another planet.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. a belt of charged particles (resulting from cosmic rays) above the Earth trapped by the Earth's magnetic field
After James Alfred Van Allen (1914-2006), American physicist.(American Heritage® Dictionary of the English Language, Fourth Edition)
From James Alfred Van Allen, US physicist. (Wiktionary)
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