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| Titel |
Electrodynamics of an omega-band as deduced from optical and magnetometer data |
| VerfasserIn |
H. Vanhamäki, K. Kauristie, O. Amm, A. Senior, D. Lummerzheim, S. Milan |
| 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 ; 27, no. 9 ; Nr. 27, no. 9 (2009-09-01), S.3367-3385 |
| Datensatznummer |
250016636
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| Publikation (Nr.) |
 copernicus.org/angeo-27-3367-2009.pdf |
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| Zusammenfassung |
We investigate an omega-band event that took place above northern Scandinavia
around 02:00–02:30 UT on 9 March 1999. In our analysis we use ground based
magnetometer, optical and riometer measurements together with satellite based
optical images. The optical and riometer data are used to estimate the
ionospheric Hall and Pedersen conductances, while ionospheric equivalent
currents are obtained from the magnetometer measurements. These data sets are
used as input in a local KRM calculation, which gives the ionospheric
potential electric field as output, thus giving us a complete picture of the
ionospheric electrodynamic state during the omega-band event.
The overall structure of the electric field and field-aligned current (FAC)
provided by the local KRM method are in good agreement with previous studies.
Also the E×B drift velocity calculated from the local
KRM solution is in good qualitative agreement with the plasma velocity
measured by the Finnish CUTLASS radar, giving further support for the new
local KRM method. The high-resolution conductance estimates allow us to
discern the detailed structure of the omega-band current system. The highest
Hall and Pedersen conductances, ~50 and ~25 S, respectively, are
found at the edges of the bright auroral tongue. Inside the tongue,
conductances are somewhat smaller, but still significantly higher than
typical background values. The electric field shows a converging pattern
around the tongues, and the field strength drops from ~40 mV/m found at
optically dark regions to ~10 mV/m inside the areas of enhanced
conductivity. Downward FAC flow in the dark regions, while upward currents
flow inside the auroral tongue. Additionally, sharp conductance gradients at
the edge of an auroral tongue are associated with narrow strips of intense
FACs, so that a strip of downward current flows at the eastern (leading) edge
and a similar strip of upward current is present at the western (trailing)
edge. The Joule heating follows the electric field pattern, so that it is
diminished inside the bright auroral tongue. |
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