Axial poloidal electromagnetic core-mantle coupling torque: A re-examination for different conductivity and satellite supported geomagnetic field models |
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| Authors: | H Greiner-Mai J Hagedoorn L Ballani I Wardinski D Stromeyer R Hengst |
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| Institution: | (1) Sec. 1.5 Earthsystem Modelling, Telegrafenberg, GeoForschungsZentrum Potsdam, 14473 Potsdam, Germany;(2) Sec. 2.3 Magnetic Field, Telegrafenberg, GeoForschungsZentrum Potsdam, 14473 Potsdam, Germany;(3) Sec. 5.3 Engineering Seismology, Telegrafenberg, GeoForschungsZentrum Potsdam, 14473 Potsdam, Germany |
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| Abstract: | We investigate the temporal behaviour of the axial component of the electromagnetic core-mantle coupling torque that is associated
with the poloidal part of the geomagnetic field observable at the Earth surface. For its computation, we use different models
of the geomagnetic field, expanded into spherical harmonics (Wardinski and Holme, 2006; Sabaka et al., 2004), and the mantle
conductivity. The geomagnetic field, which we have to know at the core-mantle boundary for the associated computations, will
be inferred from the field at the Earth surface by the non-harmonic field continuation through a conducting mantle shell.
The aims of this investigation are (i) to check how sensitive is the computation of the torque with respect to the different
geomagnetic field models, (ii) to check its dependence on the spherical harmonic degree n, and (iii) to determine the difference
between the mechanical torque derived from the observed length-of-day variations (atmospheric influence subtracted) and the
poloidal electromagnetic torque in dependence on the assumed conductivity. To use the non-harmonic field continuation for
the torque calculation and to obtain an insight into the influence of the different geomagnetic field models on the EM torques
are the major aspects of this paper.
grm@gfz-potsdam.de |
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| Keywords: | Earth’ s magnetic field core-mantle coupling torque Earth’ s rotation |
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