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magnetic pole,the two roughly opposite ends of the planet where the earth's magnetic intensity is the greatest, as the north and south magnetic poles. For the magnetic north, it is the direction from any point on the earth's surface linking the horizontal component of the magnetic lines of force with the observer and north magnetic pole; it is similar for magnetic south. The north magnetic pole, first located (1831) by British explorer Sir James C. RossRoss, Sir James Clark,
1800–1862, British polar explorer and rear admiral. In 1818 he accompanied his uncle, Sir John Ross, in search of the Northwest Passage and commanded the Erebus.
..... Click the link for more information. , has shifted over time from N Canada into the Arctic Sea near the North Pole. The south magnetic pole, reached (1909) by Australian geologists Sir T. W. E. DavidDavid, T. W. E.
(Sir Tannatt William Edgeworth), 1858–1935, Australian geologist and explorer, b. near Cardiff, Wales. David came to Australia in 1882 as an assistant geological surveyor. In 1891 he was appointed professor of geology and physical geography at the Univ.
..... Click the link for more information. and Sir Douglas MawsonMawson, Sir Douglas,
1882–1958, Australian antarctic explorer and geologist, b. England. His first geographical expedition was to the New Hebrides Islands as a geologist in 1903.
..... Click the link for more information. , is now off the Adélie Coast of Antarctica. The magnetic poles are not fixed but follow circular paths with diameters of about 100 miles (160 km). Studies of paleomagnetismpaleomagnetism,
study of the intensity and orientation of the earth's magnetic field as preserved in the magnetic orientation of certain minerals found in rocks formed throughout geologic time.
..... Click the link for more information. also indicate that the earth's magnetic field has reversed its polarity many times in the geologic past. The best hypothesis to date for the origin of terrestrial magnetism is the self-exciting dynamo theory, where the earth's magnetic field is generated by the interaction of motion and electrical currents in the earth's liquid outer core.
pole, magnetic:see magnetic polemagnetic pole,
the two roughly opposite ends of the planet where the earth's magnetic intensity is the greatest, as the north and south magnetic poles. For the magnetic north, it is the direction from any point on the earth's surface linking the horizontal component of the
..... Click the link for more information. .
a section of the surface of a magnetized object (magnet) at which the normal component of magnetization Jn is different from zero.
If the magnetic flux in a sample object and its surrounding space are represented graphically by the lines of induction of the magnetic field, the magnetic pole will correspond to the place at which the lines intersect the object’s surface. The section of the surface from which the lines of force emanate is usually called the north (N), or positive, magnetic pole; the section toward which these lines are directed is the south (S), or negative, pole. Like poles repel, and unlike poles attract. Following the analogies of the interaction of electric charges, a magnetic pole can be assigned a nonzero surface density of magnetic charges σm = Jn, although in fact there are no magnetic charges. As a result of the absence of magnetic charges in nature, the lines of magnetic induction cannot be broken in an object, and the object must always have pairs of equivalent magnetic poles of opposite polarity. Magnets and electromagnets with a large number of such pairs are used for many technical purposes (for example, in direct-current machinery).
Magnetic poles are also considered in the study of geomagnetism. The north magnetic pole of the needle of a magnetic compass indicates the direction of the earth’s north pole (or, more accurately, the earth’s south magnetic pole, which is located in the northern hemisphere), and the south pole indicates the direction of the earth’s south pole (its north magnetic pole).
REFERENCESVonsovskii, S. V. Magnetizm. Moscow, 1971.
lanovskii, B. M. Zemnoi magnetizm [3rd ed.], vol. 1. Leningrad, 1964.
a point on the earth’s surface at which the vector of induction of the earth’s magnetic field is directed vertically, downward at the north pole and upward at the south pole. Local magnetic poles are observed in the regions of certain very strong magnetic anomalies, for example, the Kursk and Eastern Siberian anomalies. The magnetic poles are close to the geographic poles.
All magnetic isogonic lines and meridians converge at the magnetic poles. The coordinates and polarity of the magnetic poles change over time; the coordinates for 1970, according to refined data, were as follows: 75.0° ± 0.5° S lat., 99.0° ± 1.0°W long, for the northern hemisphere and 66.5° ± 0.5° S lat., 140.0° ± 1.0° E long, for the southern hemisphere.
The polarity of the earth’s magnetic field in the current epoch is such that the south, or negative, magnetic pole is located in the northern hemisphere and the north, or positive, magnetic pole is located in the southern hemisphere. However, it is common practice to refer to the magnetic poles in conformity with the hemispheres in which they are located.
REFERENCESIanovskii, B. M. Zemnoi magnetizm, parts 1–2. Leningrad, 1963–64.
Medvedev, N. D. “K voprosu sovremennogo polozheniia magnitnoi osi Zemli.” Biulleten’Sovetskoi Antarkticheskoi ekspeditsii, 1972, no. 84, p. 89.