Can depression of the core-mantle interface cause coincident Magsat and geoidal ‘lows’ of the Central Indian Ocean?

Abstract

According to Hide, undulations at the core-mantle interface distort geopotential fields that can be observed in lower order harmonics. Hide and Malin obtained a significant correlation between long wavelength gravity and non-dipole magnetic fields, when the latter is displaced in longitude by 160°. The Central Indian Ocean is characterised by the largest geoidal low, which correlates well with the Magsat component low without any longitudinal displacement. An integrated interpretation of geoidal and magnetic anomalies suggests that the source of these anomalies should be the same and may originate at the depression of the core-mantle boundary. The shallow Curie-isotherm, the matching of the long wavelength of the geoidal anomaly with the vertical Magsat anomaly and the identical location of the centres of the anomalies, provide an excellent confirmation of Hide's hypothesis, but contradicts earlier geoidal low interpretations of mass deficiency in the Earth's crust and mantle.