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| Titel |
Ionospheric conductance distribution and MHD wave structure: observation and model |
| VerfasserIn |
F. Budnik, M. Stellmacher, K.-H. Glassmeier, S. C. Buchert |
| 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 ; 16, no. 2 ; Nr. 16, no. 2, S.140-147 |
| Datensatznummer |
250013150
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| Publikation (Nr.) |
 copernicus.org/angeo-16-140-1998.pdf |
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| Zusammenfassung |
The ionosphere influences magnetohydrodynamic
waves in the magnetosphere by damping because of Joule heating and by varying
the wave structure itself. There are different eigenvalues and eigensolutions of
the three dimensional toroidal wave equation if the height integrated Pedersen
conductivity exceeds a critical value, namely the wave conductance of the
magnetosphere. As a result a jump in frequency can be observed in ULF pulsation
records. This effect mainly occurs in regions with gradients in the Pedersen
conductances, as in the auroral oval or the dawn and dusk areas. A pulsation
event recorded by the geostationary GOES-6 satellite is presented. We explain
the observed change in frequency as a change in the wave structure while
crossing the terminator. Furthermore, selected results of numerical simulations
in a dipole magnetosphere with realistic ionospheric conditions are discussed.
These are in good agreement with the observational data.
Key words. Ionosphere · (Ionosphere · magnetosphere
interactions) · Magnetospheric physics · Magnetosphere · ionosphere
interactions · MHD waves and instabilities. |
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