The Magnetic Field of the Earth’s Lithosphere

Abstract

The lithospheric contribution to the Earth's magnetic field is concealed in magnetic field data that have now been measured over several decades from ground to satellite altitudes. The lithospheric field results from the superposition of induced and remanent magnetisations. It therefore brings an essential constraint on the magnetic properties of rocks of the Earth's sub-surface that would otherwise be difficult to characterize. Measuring, extracting, interpreting and even defining the magnetic field of the Earth's lithosphere is however challenging. In this paper, we review the difficulties encountered. We briefly summarize the various contributions to the Earth's magnetic field that hamper the correct identification of the lithospheric component. Such difficulties could be partially alleviated with the joint analysis of multi-level magnetic field observations, even though one cannot avoid making compromises in building models and maps of the magnetic field of the Earth's lithosphere E. Thébault ( ) 96 E. Thébault et al.at various altitudes. Keeping in mind these compromises is crucial when lithospheric field models are interpreted and correlated with other geophysical information. We illustrate this discussion with recent advances and results that were exploited to infer statistical properties of the Earth's lithosphere. The lessons learned in measuring and processing Earth's magnetic field data may prove fruitful in planetary exploration, where magnetism is one of the few remotely accessible internal properties.

Post-processing scheme for modelling the lithospheric magnetic field

“…The final resulting model of the lithospheric field is nonetheless of high quality and compares well with other recently released models (e.g. MF7 that is not published but the MF6 is presented in Maus et al (2008); CHAOS-4; Olsen et al, 2010b) as well as older models (see for a review Thébault et al, 2010).…”

Measuring the Earth’s Magnetic Field from Space: Concepts of Past, Present and Future Missions

“…This led in particular to a continuous stream of ever improving models of the lithospheric field (for a recent review, see e.g. Thébault et al 2010), and of the core field, the time variations of which are now monitored with unprecedented accuracy (see e.g. .…”

“…Olsen et al (2010b), and recent reviews providing even more information about the fields produced can be found in e.g. Hulot et al (2007), Jackson and Finlay (2007), , for the core field, Purucker and Whaler (2007), Thébault et al (2010) for the lithospheric field, Manoj et al (2006), Maus (2007b), Kuvshinov (2008) for the field produced within the oceans, Kivelson and Russell (1995), Kelley (2009) for the field of external origin, and Constable (2007), Kuvshinov (2008) for externally induced internal fields.…”

“…Reports on these progress and currently developing methodologies can be found in many books and reviews, such as e.g. Langel (1987), Langel and Hinze (1998), , , Hulot et al (2007, Thébault et al (2010), , Olsen et al (2010a). Also, even though these progress have led to some improvement in the recovery of the field of external origin, the identification of local sources at LEO satellite altitude (e.g.…”

The Earth’s Magnetic Field in the Space Age: An Introduction to Terrestrial Magnetism

“…In a complementary way, Olsen et al (2010b) next describe satellite concepts that have been used, will be used, or could be envisaged for measuring the Earth's magnetic field from space. The way these data can be processed to recover the lithospheric field (Thébault et al 2010) and the time-varying core field ) are next discussed. Although many aspects of short-term core dynamics can now be observed, their interpretation is still lagging and remains the subject of much debate.…”