Earth's magnetic field, also known as the
geomagnetic field, is the
magnetic field that extends from the
Earth's interior to where it meets the
solar wind, a stream of
charged particles emanating from the
Sun. Its magnitude at the Earth's surface ranges from 25 to 65
microteslas (0.25 to 0.65
gauss). Roughly speaking it is the field of a
magnetic dipole currently tilted at an angle of about 10 degrees with respect to
Earth's rotational axis, as if there were a
bar magnet placed at that angle at the center of the Earth. Unlike a bar magnet, however, Earth's magnetic field changes over time because it is generated by a
geodynamo (in Earth's case, the motion of molten iron alloys in its
outer core).