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| Titel |
Numerical analysis of global ionospheric current system including the effect of equatorial enhancement |
| VerfasserIn |
S. Tsunomura |
| 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 ; 17, no. 5 ; Nr. 17, no. 5, S.692-706 |
| Datensatznummer |
250013751
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| Publikation (Nr.) |
 copernicus.org/angeo-17-692-1999.pdf |
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| Zusammenfassung |
A modeling method is proposed to derive a
two-dimensional ionospheric layer conductivity, which is appropriate to obtain a
realistic solution of the polar-originating ionospheric current system including
equatorial enhancement. The model can be obtained by modifying the conventional,
thin shell conductivity model. It is shown that the modification for one of the
non-diagonal terms (Σθφ) in the
conductivity tensor near the equatorial region is very important; the term
influences the profile of the ionospheric electric field around the equator
drastically. The proposed model can reproduce well the results representing the
observed electric and magnetic field signatures of geomagnetic sudden
commencement. The new model is applied to two factors concerning
polar-originating ionospheric current systems. First, the latitudinal profile of
the DP2 amplitude in the daytime is examined, changing the canceling rate for
the dawn-to-dusk electric field by the region 2 field-aligned current. It is
shown that the equatorial enhancement would not appear when the ratio of the
total amount of the region 2 field-aligned current to that of region 1 exceeds
0.5. Second, the north-south asymmetry of the magnetic fields in the summer
solstice condition of the ionospheric conductivity is examined by calculating
the global ionospheric current system covering both hemispheres simultaneously.
It is shown that the positive relationship between the magnitudes of high
latitude magnetic fields and the conductivity is clearly seen if a voltage
generator is given as the source, while the relationship is vague or even
reversed for a current generator. The new model, based on the International
Reference Ionosphere (IRI) model, can be applied to further investigations in
the quantitative analysis of the magnetosphere-ionosphere coupling problems.
Key words. Ionosphere (electric fields and currents;
equatorial ionosphere; ionosphere-magnetosphere interactions) |
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