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Shown here is the difference between the variations of horizontal intensity
(H), declination (D) and vertical intensity (Z) at the observatories
Niemegk and Wingst. Addition of the difference between a moving average
values gives the absolute differences.
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The average absolute difference is approximatly the difference of field
contributions from inside the Earth: the slowly varying main field
originating in the Earth's outer core and local, constant field
contributions due to magnetized rocks in the Earth's crust (crustal field).
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Differences in the variations reflect the inhomogeneity of the field
contributions with sources external to Earth in the ionosphere and
magnetosphere. During magnetically quiet times the differences vary only
slightly as the fields are close to homogeneous over the distance
Niemegk - Wingst. During magnetically disturbed conditions the differences
can vary with considerable amplitudes. In particular geomagnetic storms show
large inhomogeneity.
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The differences have different information content in the individual
components. Horizontal intensity is most directly influenced by the
external field contributions. Variations in vertical intensity are strongly
influenced by the electrical conductivity of the subsurface and contain
information on the field contributions induced in the Earth by the external
variations.
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Strong short-period differences in Z between Niemegk and
Wingst often are a result from the fact that variations of certain periods
have the opposite sign at the two observatories in this component.
The different behaviour of horizontal and vertical components can be used to
study the conductivity distribution inside the Earth, for example by
magnetotellurics.
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The values shown here are calculated from uncorrected measurement results.
Sporadically artificial disturbances (i.e. erroneous values) might occur,
which will only be corrected in the final data sets later on. Such irregular
errors may be able to distort the scaling.
