'magnetosphere' definitions:

Definition of 'magnetosphere'

From: WordNet
noun
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

Definition of 'magnetosphere'

From: GCIDE
  • 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]