Earth’s magnetic field (arrowed lines) is similar to that produced by a bar magnet. The dotted lines at the centre of the diagram represent the processes in the earth's core that produce a magnetic field. The arrows represent invisible lines of force, known as magnetic field lines. They indicate the direction a compass arrow lies – pointing north–south.

The magnetic axis (the yellow line between the magnetic north and south poles) is at an angle to earth’s rotational axis (the green line between the geographic north and south poles). Consequently true north (the North Pole) is at some distance from magnetic north. Compass directions need to be corrected for the difference between true north and magnetic north. This difference is called magnetic declination.

Base map: NASA Visible Earth