3-D Global Induction in the Oceans and Solid Earth: Recent Progress in Modeling Magnetic and Electric Fields from Sources of Magnetospheric,Ionospheric and Oceanic Origin |
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Authors: | A V Kuvshinov |
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Institution: | (1) Institute of Geophysics, ETH, 8093 Zurich, Switzerland |
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Abstract: | Electromagnetic induction in the Earth’s interior is an important contributor to the near-Earth magnetic and electric fields.
The oceans play a special role in this induction due to their relatively high conductivity which leads to large lateral variability
in surface conductance. Electric currents that generate secondary fields are induced in the oceans by two different processes:
(a) by time varying external magnetic fields, and (b) by the motion of the conducting ocean water through the Earth’s main
magnetic field. Significant progress in accurate and detailed predictions of the electric and magnetic fields induced by these
sources has been achieved during the last few years, via realistic three-dimensional (3-D) conductivity models of the oceans,
crust and mantle along with realistic source models. In this review a summary is given of the results of recent 3-D modeling
studies in which estimates are obtained for the magnetic and electric signals at both the ground and satellite altitudes induced
by a variety of natural current sources. 3-D induction effects due to magnetospheric currents (magnetic storms), ionospheric
currents (Sq, polar and equatorial electrojets), ocean tides, global ocean circulation and tsunami are considered. These modeling
studies demonstrate that the 3-D induction (ocean) effect and motionally-induced signals from the oceans contribute significantly
(in the range from a few to tens nanotesla) to the near-Earth magnetic field. A 3-D numerical solution based on an integral
equation approach is shown to predict these induction effects with the accuracy and spatial detail required to explain observations
both on the ground and at satellite altitudes.
On leave from Institute of Terrestrial Magnetism, Ionosphere and Radiowave Propagation, Russian Academy of Sciences, 142190
Troitsk, Moscow region, Russia. |
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Keywords: | Global EM induction 3-D numerical modeling Ocean effect Magnetospheric and ionospheric sources Ocean tides Global ocean circulation Tsunami |
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