(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
The Collaborative International Dictionary of English (GCIDE) v.0.53 Collaborative International Dictionary (GCIDE)
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 ]