Earth’s Magnetic Dipole

Earth’s Magnetic Dipole

. The Earth’s magnetic field looks like that which would be produced by a bar magnet at the center of the Earth, with the North Magnetic Pole corresponding to the South Geographic Pole and vice versa. It originates in swirling currents of molten iron deep in the Earth’s core, and extends more than 20 Earth radii, or 126,000 meters out into space. Magnetic field lines loop out of the South Geographic Pole and into the North Geographic Pole. A compass needle will always point along a field line. The lines are close together near the magnetic poles where the magnetic force is strong, and spread out where it is weak. The magnetic axis is tilted at an angle of 11.7 degrees with respect to the Earth’s rotational axis. Notice that the poles of the magnet are inverted with respect to the geographic poles, following the custom of defining positive, north magnetic polarity as the one in which magnetic fields point out, and negative, south magnetic polarity as the place where magnetic fields point in. This dipolar (two poles) configuration applies near the surface of the Earth, but further out the magnetic field is distorted by the solar wind.

Copyright 2010, Professor Kenneth R. Lang, Tufts University