Planet Earth and Geomagnetism essays

Planet Earth and Geomagnetism essays Geomagnetism refers to the study of earth's magnetism. Generation of the magnetic field appears to be related to the motion of fluid upon the earth. "It electrically conducts the material within the earth, and the planet acts as a self-exciting dynamo" [Encarta Encyclopedia 1998]. The conducting material and the geomagnetic field may mutually control each other. Study of this theory is called magnetohydrodynamics or hydromagnetics. The study of how the magnetic field Ha changed throughout the earth's history, called paleomagnetism, provided the first strong theories of plate tectonics. More proof of this theory is the fact that the surface of the earth has a negative charge. Although the conductivity of the air near the earth is small, air is not a perfect insulator, and the negative charge would drain off quickly if it were not continuously replenished in some way. The magnetic poles do not correspond with the geographic poles of its axis, and the position of the magnetic poles is not constant and shows an appreciable change from year to year. Variations in the magnetic field of the earth include secular variation - the change in the direction of the field caused by shifting of the poles. This is a periodic variation that repeats itself after 960 years. A smaller annual variation also exists, as does diurnal, or daily, which can only be detected by sensitive instruments. Measurements of the secular variation show that the entire magnetic field has a tendency to drift westward at the rate of 12 - 15 miles per year. There is also the theoretical elementary particle containing only one magnetic pole; it is called a monopole. All known magnetic particles are dipole in nature - that is, they contain both a "north" and "south" magnetic pole - but the possible existence of magnetic monopoles was proposed by symmetry theories in the 1930's. This idea remains part of currents grand unification theories that are attempting to bring togeth...