Magnetosphere

photo: Artistic rendition of Magnetosphere.

A magnetosphere is the region around an astronomical object in which phenomena are dominated or organized by its magnetic field. Earth is surrounded by a magnetosphere, as are the magnetized planets Mercury, Jupiter, Saturn, Uranus and Neptune. Jupiter's moon Ganymede is magnetized, but too weakly to trap solar wind plasma. Mars has patchy surface magnetization. The term "magnetosphere" has also been used to describe regions dominated by the magnetic fields of celestial objects, e.g. pulsar magnetospheres.