A planetary magnetic field. Not all planets have a magnetosphere. In terrestrial-type planets it is cause by the molten iron-nickel core and aligned with the north and south poles, and helps to shield against cosmic radiation. The magnetosphere extends some distance into space (depending on the strength of the local planetary magnetism) and is influenced by the solar wind. It is teardrop shaped - being longer in the side facing away from the Sun (the magnetotail.)
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Development Notes
Text by M. Alan Kazlev
Initially published on 08 December 2001.