Unraveling the Magnetic Mystery of the Earth’s Lithosphere: The Background and the Role of the CHAMP Mission

Summary

The utility of high-resolution aeromagnetic surveys in geologic mapping is well known. As the wavelength of anomalies increases, geologic interpretation becomes less direct and the magnetic response of geology more complex. The long wavelength magnetic anomalies observed at the altitudes of near-Earth satellites represent the collective effect of many contiguous regional-scale geologic units. The variations also reflect the effect of the Curie isotherm that governs the thickness of the magnetic crust, and therefore may be used to constrain the models of regional variations of heat flow. This information in turn can be useful in deriving lithospheric strength variations and also constraining models of global seismological parameters. The challenge of the CHAMP magnetic experiment is to unravel this complex information beyond the level of Magsat and extract from it new knowledge regarding the Earth’s lithosphere that could be used by geologists and geophysicists. There are a number of fronts along which improvements appear possible in the anomaly field and their interpretation from the overall mission characteristics of the CHAMP satellite. They are: improvements due to data redundancy and attitude determinations, better external field models, increased anomaly resolution during late-phase lower altitude part of the mission, new direct interpretation techniques and, taking advantage of gravity field from the CHAMP mission, improved interpretations resulting from correlations with gravity anomaly data through Poisson’s relation. Magnetic anomaly data provide a unique perspective on geologic processes as evident from the well known example of magnetic stripes associated with the seafloor spreading—a process that could not be inferred readily through other geophysical quantities. Similarly, information on bulk geologic variations of size greater than a few hundred km is difficult to obtain through routine geologic techniques. This is the scale at which satellite magnetic and gravity data from CHAMP can find its niche in the lithospheric interpretation.