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| Titel |
Ionospheric currents estimated simultaneously from CHAMP satelliteand IMAGE ground-based magnetic field measurements: a statisticalstudy at auroral latitudes |
| VerfasserIn |
P. Ritter, H. Lühr, A. Viljanen, O. Amm, A. Pulkkinen, I. Sillanpää |
| 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. 2 ; Nr. 22, no. 2 (2004-01-01), S.417-430 |
| Datensatznummer |
250014772
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| Publikation (Nr.) |
 copernicus.org/angeo-22-417-2004.pdf |
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| Zusammenfassung |
One important contribution to the magnetic field measured at
satellite altitude and at ground level comes from the external
currents. We used the total field data sampled by the Overhauser
Magnetometer on CHAMP and the horizontal magnetic field
measurements of the IMAGE ground-based magnetometer network to
study the ionospheric Hall current system in the auroral regions.
For the CHAMP data a current model consisting of a series of lines
and placed at a height of 110km is fitted to the magnetic field
signature sampled on the passage across the polar region. The
derived current distributions depend, among others, on season and
on the local time of the satellite track. At dawn/dusk the auroral
electrojets can be detected most clearly in the auroral
regions. Their intensity and location are evidently correlated
with the A E activity index. For a period of almost two years the
results obtained from space and the currents determined from
ground-based observations are studied. For the full IMAGE station
array a newly-developed method of spherical elementary current
systems (SECS) is employed to compute the 2-D equivalent current
distribution, which gives a detailed picture of an area covering
latitudes 60° – 80° N and 10° – 30° E in the
auroral region. Generally, the current estimates from satellite
and ground are in good agreement. The results of this survey
clearly show the average dependence of the auroral electrojet on season and local
time. This is particularly true during periods of increased
auroral activity. The correlation coefficient of the results is
close to one in the region of sizeable ionospheric current
densities.
Also the ratio of the current densities, as determined from above
and below the ionosphere, is close to unity. It is the first time
that the method of Hall current estimate from a satellite has been
validated quantitatively by ground-based observations. Among
others, this result is of interest for magnetic main field
modelling, since it demonstrates that ground-based observations
can be used to predict electrojet signatures in satellite magnetic
field scalar data.
Key words. Ionosphere (auroral Ionosphere; electric fields
and currents; ionosphere-magnetosphere interactions) |
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