Magnetic potential and magnetization contrasts of Earth's lithosphere

An inversion technique is developed in order to transform a global scalar magnetic anomaly map into a global magnetic susceptibility contrast map which delineates the magnetic characteristics of the lithosphere. The inversion involves two stages. In the first stage, a scalar magnetic anomaly map is transformed into a magnetic potential map. This stage requires no simplifying assumption, and it provides a means to upward/downward continue global scalar magnetic anomaly maps. In the second stage, the potential map is inverted into a magnetic susceptibility contrast map of the lithosphere based on the assumption that the magnetization is of induced origin. The magnetization of the continental crust that gives rise to satellite magnetic anomalies is largely of induced origin. It is also shown that the magnetization direction of the oceanic lithosphere does not differ significantly from the direction of the present core field, except in a few limited areas, supporting the assumption made about the induced magnetization of the lithosphere. The technique is applied to the scalar magnetic anomaly map of Earth derived using POGO and Magsat data. The resulting susceptibility contrasts directly correlate with geological features and better delineate small-scale features due to the enhancement of the higher-degree harmonics compared to the lower-degree ones.