Dictionary
mag•ne•to•sphere
Pronunciation: (mag-nē'tu-sfēr"), [key]—
n. Astron.
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.