The earth itself acts like a huge magnet. It is not known exactly why the earth is a magnet, it is not a magnetized chunk of iron like a bar magnet, and is too hot for individual atoms to remain aligned.

Magnetic Declination

The north pole of a magnet seeks out the north pole of the earth and vice verse with the south pole.
The magnetic pole in the northern hemisphere is located nearly 1800 kilometers from the geographical north pole, the other magnetic pole is located south of Australia. Which means compasses do not generally point to true north. This disagreement between this arrangement of a compass and true north is known as the magnetic declination

A dipping Needle indicates the direction of the earths magnetic equator, it is a magnetized needle mounted on a horizontal pivot so that it can swing up and down freely.

Phenomena

Only a few of the phenomena observed on the ground come from the magnetosphere: fluctuations of the magnetic field known as magnetic storms and substorms, and the polar aurora or "northern lights," appearing in the night skies of places like Alaska and Norway. Satellites in space, however, sense much more: radiation belts, magnetic structures, fast streaming particles and processes which energize them.

Unstable Magnetic field

The earths magnetic field begins at an altitude of about 1000 kilometers and extends to about 64,000 kilometers in space.

The magnetic field of the earth is not stable; it has wanderd through out geological time. this evidence was found by testing the orientation of the domains in the rock. The evidence showed there had been times when the magnetic field of the earth had diminished to zero and then reversed itself. Studies of deep-sea sediments indicate that more than twenty reversals have occured.

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