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| Titel |
Applying inversion techniques to derive source currents and geoelectric fields for geomagnetically induced current calculations |
| VerfasserIn |
J. S. de Villiers, P. J. Cilliers |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 32, no. 10 ; Nr. 32, no. 10 (2014-10-16), S.1263-1275 |
| Datensatznummer |
250121120
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| Publikation (Nr.) |
 copernicus.org/angeo-32-1263-2014.pdf |
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| Zusammenfassung |
| This research focuses on the inversion of geomagnetic variation field
measurement to obtain source currents in the ionosphere. During a geomagnetic
disturbance, the ionospheric currents create magnetic field variations that
induce geoelectric fields, which drive geomagnetically induced currents (GIC)
in power systems. These GIC may disturb the operation of power systems and
cause damage to grounded power transformers. The geoelectric fields at any
location of interest can be determined from the source currents in the
ionosphere through a solution of the forward problem. Line currents running
east–west along given surface position are postulated to exist at a certain
height above the Earth's surface. This physical arrangement results in the
fields on the ground having the magnetic north and down components, and the
electric east component. Ionospheric currents are modelled by inverting
Fourier integrals (over the wavenumber) of elementary geomagnetic fields
using the Levenberg–Marquardt technique. The output parameters of the
inversion model are the current strength, height and surface position of the
ionospheric current system. A ground conductivity structure with five layers
from Quebec, Canada, based on the Layered-Earth model is used to obtain the
complex skin depth at a given angular frequency. This paper presents
preliminary and inversion results based on these structures and simulated
geomagnetic fields. The results show some interesting features in the
frequency domain. Model parameters obtained through inversion are within
2% of simulated values. This technique has applications for modelling
the currents of electrojets at the equator and auroral regions, as well as
currents in the magnetosphere. |
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