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| Titel |
On the ionospheric coupling of auroral electric fields |
| VerfasserIn |
G. T. Marklund |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1023-5809
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| Digitales Dokument |
URL |
| Erschienen |
In: Nonlinear Processes in Geophysics ; 16, no. 2 ; Nr. 16, no. 2 (2009-04-30), S.365-372 |
| Datensatznummer |
250013146
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| Publikation (Nr.) |
 copernicus.org/npg-16-365-2009.pdf |
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| Zusammenfassung |
| The quasi-static coupling of high-altitude potential structures and electric
fields to the ionosphere is discussed with particular focus on the downward
field-aligned current (FAC) region. Results are presented from a preliminary
analysis of a selection of electric field events observed by Cluster above
the acceleration region. The degree of coupling is here estimated as the
ratio between the magnetic field-aligned potential drop, ΔΦII, as inferred from the characteristic energy of upward ion
(electron) beams for the upward (downward) current region and the
high-altitude perpendicular (to B) potential, ΔΦbot, as calculated by integrating the perpendicular electric field
across the structure. For upward currents, the coupling can be expressed
analytically, using the linear current-voltage relation, as outlined by
Weimer et al. (1985). This gives a scale size dependent coupling where
structures are coupled (decoupled) above (below) a critical scale size. For
downward currents, the current-voltage relation is highly non-linear which
complicates the understanding of how the coupling works. Results from this
experimental study indicate that small-scale structures are decoupled,
similar to small-scale structures in the upward current region. There are,
however, exceptions to this rule as illustrated by Cluster results of
small-scale intense electric fields, correlated with downward currents,
indicating a perfect coupling between the ionosphere and Cluster altitude. |
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