Geophysical Implications of the Interrelationship of the Geogravity and Geomagnetic Fields

Abstract

RECENTLY there has been much interest in the geophysical implications of the satellite-determined gravity field, and one suggestion is that the low-degree gravity harmonics are associated with undulations at the core–mantle boundary1–4. Mathematical formulation5 does indicate that any mass anomalies at the core–mantle boundary would be observable in the Earth's external potential. Indirect evidence in favour of this hypothesis would come from a strong correlation between the gravity and geomagnetic fields, because variations in the latter are attributed to sources located in the outer core. Egyed3 pointed out a positive correlation between the satellite geoid6 and the geomagnetic secular variations7, but Coode and Runcorn8 showed that this correlation was negligible when an improved satellite geoid9 was used. Hide4 has proposed, however, that certain magnetohydrodynamical considerations may suggest low amplitude, long wavelength irregularities in the core–mantle interface.