On variations of the geomagnetic field, fluid motions, and the rate of the Earth's rotation

Estimated time-fluctuations in the rate of westward drift of the geomagnetic field, 1885–1945, are shown to correspond reasonably well with the unexplained systematic fluctuations in the earth's rate of rotation derived by Brouwer. In view of other geophysical evidence on the rigidity of the earth, it appears reasonable to conclude (1) that the source of the geomagnetic field lies within a large-scale fluid circulation inside the central core of the earth; and (2) that this fluid circulation in the core must be considered established as real, since no other adequate large source needed to conserve angular momentum is apparently available. As an independent check, a smaller time-fluctuation derived from the northerly drift of the geomagnetic field may afford, through the associated fluid motion, an explanation of the non-seasonal departures observed in the variation of latitude, yielding an estimated angular momentum transverse to the axis of rotation.