See also: In-depth

The North Magnetic Pole is the point on the Earth's surface where the magnetic field is directed vertically downward. Based on this simple definition the North Magnetic Pole also has the following properties:

• Inclination is 90°
• Horizontal intensity is 0 nT
• Magnetic meridians, lines tracing the path one would take by following a compass needle, converge on the Magnetic Pole
• Lines of equal magnetic declination also converge on the Pole; therefore declination is undefined at the Pole

As an aid to understanding the definition and properties of the Magnetic Pole it is useful to look at the magnetic field produced by a simple bar magnet. The magnetic field around a simple bar magnet can be visualized in terms of "lines of force", or "magnetic field lines"; these are commonly illustrated by iron filings sprinkled on a sheet of paper held over the magnet. Field lines start near one end of the magnet and enter near the other end, forming an arc in between. By convention, the end at which the magnetic field is directed outward is termed the "north" pole of the magnet; the end at which the magnetic field is directed inward is termed the "south" pole of the magnet. The magnetic field of a bar magnet is called a "dipole" field, so named because it has two poles.

To a first approximation the Earth's magnetic field is a dipole field. You can visualize it being produced by an imaginary bar magnet placed at the Earth's centre. Consequently the definition of poles, established for a bar magnet, has been applied to the magnetic field of the Earth. However, the shape of the Earth's magnetic field is much more complex than that of a simple dipole, and as a result the observed positions of the magnetic poles are displaced a considerable distance from the end-points of the imaginary bar magnet. The complexity of the magnetic field has another important consequence: a compass does not point directly at the North Magnetic Pole. If you set out following your compass needle you will eventually reach the Pole, but not by the most direct route.

The magnetic field is directed downward in the northern hemisphere and upward in the southern hemisphere. This implies that the magnetic pole in the Canadian Arctic is really a "south pole". However, by long custom and because of its geographical location it is called the North Magnetic Pole.