Comparison of Estimates of Surface Fluid Motions of the Earth's Core for Various Epochs.
The velocity patterns of the fluid at the surface of the earth's core are compared for different epochs since 1885. The velocity of the fluid at the surface of the earth's core can be related to the magnetic field and its secular change through hydromagnetic equations. The velocity patterns for epoch 1960 show an upflow in southern Africa and a downflow in the Pacific, and four horizontal rotational cells, corresponding roughly to geostrophic flow around the vertical flow. The westward drift is somewhat smaller than that found previously. Comparison of the velocity patterns at epochs 1885, 1912, 1933, and 1960 shows the African upflow to be a strikingly persistent feature.