The concept of equating the drift of the geomagnetic field with a similar drifting motion of the earth's core is examined. The drift of the field at the earth's surface and at the core is calculated, and the two values are shown to be considerably different. Analysis of the portion of secular change remaining after westward drift effects have been removed is used to provide an estimate of the error in the drift which results from equating the drift of the field to that of the core. On this basis the best estimate of the westward drift of the core for epoch 1960 is found to be 0.13 degrees per year, with an estimated error of + 0.03 degrees per year. This drift is considerably smaller than the values usually cited for the core's rotation, such as 0.18 degrees per year obtained by Bullard and others, based mainly on charted differences in surface data. 21 pp. Refs. (Author)
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