Figure 1.

The Earth’s magnetic field and its components

(A) The Earth is surrounded by a static magnetic field that is believed to result from movement of the iron core at its center. The magnetic field lines emanate from the magnetic North Pole (mN) in the southern hemisphere and enter the Earth at the magnetic South Pole (mS) in the northern hemisphere. The intensity of the magnetic field is proportional to the distance between the magnetic field lines. The intensity gradient on the planet ranges from ∼65 μT at the poles to ∼25 μT at the equator.

(B) The inclination of the Earth’s magnetic field is defined as the angle between the magnetic field lines and the Earth’s surface, which changes from ∼90° at the poles to 0° at the magnetic equator.