magnetosphere

from WordNet (r) 3.0 (2006)

magnetosphere
    n 1: the magnetic field of a planet; the volume around the
         planet in which charged particles are subject more to the
         planet's magnetic field than to the solar magnetic field

from The Collaborative International Dictionary of English v.0.48

magnetosphere \mag*net"o*sphere\, n.
   the magnetic field of a planet; the volume around the planet
   in which charged particles are subject more to the planet's
   magnetic field than to the solar magnetic field.
   [WordNet 1.6]

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