Satellite Geoid and the Structure of the Earth

Abstract

PROF. EGYED postulates1 that harmonics of low degree of the geopotential arise from undulations of the core–mantle interface, and argues that the correspondence between highs and lows of the geoid surface and the isoporic foci of the vertical component of the geomagnetic field support this view. This argument is surely untenable. First, the correlation between magnetic and gravity fields is weak. This may be shown using either of Izsak's geoids2,3 and the secular variation of the vertical (Z) or the eastward horizontal (Y) components of the geomagnetic secular variation field for the epoch 1942.5, given by Vestine et al.4. Values of the geoid heights and the magnetic field components were taken at corresponding 10° intervals. A weak correlation exists between the Y-components and the ‘old’ geoid but no correlation between any of the others: Only the Z and the Y isopores were chosen because all other geomagnetic maps, whether isoporic or not, do not correlate as well.