  We provide a space domain oriented separation of magnetic fields into parts
generated by sources in the exterior and sources in the interior of a given
sphere. The separation itself is well-known in geomagnetic modeling, usually in
terms of a spherical harmonic analysis or a wavelet analysis that is spherical
harmonic based. In contrast to these frequency oriented methods, we use a more
spatially oriented approach in this paper. We derive integral representations
with explicitly known convolution kernels. Regularizing these singular kernels
allows a multiscale representation of the internal and external contributions
to the magnetic field with locally supported wavelets. This representation is
applied to a set of CHAMP data for crustal field modeling.
