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| Titel |
Propagation of ULF waves through the ionosphere: Inductive effect for oblique magnetic fields |
| VerfasserIn |
M. D. Sciffer, C. L. Waters, F. W. Menk |
| 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 ; 22, no. 4 ; Nr. 22, no. 4 (2004-04-02), S.1155-1169 |
| Datensatznummer |
250014830
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| Publikation (Nr.) |
 copernicus.org/angeo-22-1155-2004.pdf |
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| Zusammenfassung |
Solutions for ultra-low frequency (ULF) wave fields in the frequency range
1–100mHz that interact with the Earth's ionosphere in the presence of
oblique background magnetic fields are described. Analytic expressions for
the electric and magnetic wave fields in the magnetosphere, ionosphere and
atmosphere are derived within the context of an inductive ionosphere. The
inductive shielding effect (ISE) arises from the generation of an
"inductive" rotational current by the induced part of the divergent electric
field in the ionosphere which reduces the wave amplitude detected on the
ground. The inductive response of the ionosphere is described by Faraday's
law and the ISE depends on the horizontal scale size of the ULF disturbance,
its frequency and the ionosphere conductivities. The ISE for ULF waves in a
vertical background magnetic field is limited in application to high
latitudes. In this paper we examine the ISE within the context of oblique
background magnetic fields, extending studies of an inductive ionosphere and
the associated shielding of ULF waves to lower latitudes. It is found that
the dip angle of the background magnetic field has a significant effect on
signals detected at the ground. For incident shear Alfvén mode waves and
oblique background magnetic fields, the horizontal component of the field-aligned
current contributes to the signal detected at the ground. At low
latitudes, the ISE is larger at smaller conductivity values compared with
high latitudes.
Key words. Ionosphere (ionosphere-magnetosphere interactions;
electric fields and currents; wave propagation) |
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