The Magnetic Field of the Earth's Lithosphere

Research areas:
Space Sci. Rev.
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 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.