Mercury's magnetic field and large core

Mercury

. The magnetic field of Mercury is a miniature version of Earth's magnetic field, complete with bow shock, magnetosphere and magnetotail. Mercury's magnetic axis is closely aligned with its rotation axis, and its polarity is the same as the Earth's, with magnetic north corresponding to geographic north. This magnetic field is probably generated within the planet's large iron core, which takes up three-quarters of the planet's radius, but the exact mechanism for creating the field remains a mystery. The electrified solar wind compresses the magnetic field into a bow shock on the sunlit side and draws it out into a tail on the opposite side.

Copyright 2010, Professor Kenneth R. Lang, Tufts University