Abstract

Three methods are used to determine a 1975 position for the north magnetic dip pole. A cubic polynomial in the horizontal components X (north) and Y (east) is fitted by least squares to 3050 component observations in an area of 2.65 × 106 km2 around the pole. A second analysis, in grid components U (north) and V (east), is carried out on 1394 component observations in a smaller area of 106 km2. In the third analysis, a linear fit is made to data obtained from four stations operating during a special survey of the dip pole region in 1973. The mean position adopted for 1975.0 is 76.2°N, 100.6°W.The present secular motion of the dip pole is 11 km/year north and 3 km/year west. Its secular motion has been mainly northward for the past 75 years. Plots of the diurnal motion of the dip pole show that on an average disturbed day, the pole may be as much as 65 km from its mean position.

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