Pronunciation: (mag-nē'tu-sfēr"), [key]
1. the outer region of the earth's ionosphere, where the earth's magnetic field controls the motion of charged particles, as in the Van Allen belts. Cf. magnetopause.
2. such a region of another planet: Jupiter's magnetosphere.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.