It is attracted to the geographic North Pole, which is a magnetic south pole (opposite magnetic poles attract). The north pole of a compass needle is a magnetic north pole. Interaction of the terrestrial magnetic field with particles from the solar wind sets up the conditions for the aurora phenomena near the poles. Venus's rotation period of 243 Earth days is just too slow to produce the dynamo effect. Mariner 2 found that Venus does not have such a magnetic field although its core iron content must be similar to that of the Earth.
Evidence for 171 magnetic field reversals during the past 71 million years has been reported.Īlthough the details of the dynamo effect are not known in detail, the rotation of the Earth plays a part in generating the currents which are presumed to be the source of the magnetic field. Rock specimens of different age in similar locations have different directions of permanent magnetization. The Earth's magnetic field is attributed to a dynamo effect of circulating electric current, but it is not constant in direction. The magnitude varies over the surface of the Earth in the range 0.3 to 0.6 Gauss. The magnetic field magnitude measured at the surface of the Earth is about half a Gauss and dips toward the Earth in the northern hemisphere. A current loop gives a field similar to that of the earth. Magnetic fields surround electric currents, so we surmise that circulating electic currents in the Earth's molten metalic core are the origin of the magnetic field. So how did the Earth get its magnetic field? The Earth's coreis hotter than that and therefore not magnetic. The problemwith that pictureis that the Curie temperature of iron is about 770 C. The Earth's magnetic field is similar tothat of a bar magnettilted 11 degrees from thespin axis of the Earth. Magnetic Field of the Earth Magnetic Field of the Earth
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