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| Titel |
Thermospheric density structures over the polar regions observed with CHAMP |
| VerfasserIn |
K. Schlegel, H. Lühr, J.-P. St.-Maurice, G. Crowley, C. Hackert |
| 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 ; 23, no. 5 ; Nr. 23, no. 5 (2005-07-28), S.1659-1672 |
| Datensatznummer |
250015255
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| Publikation (Nr.) |
 copernicus.org/angeo-23-1659-2005.pdf |
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| Zusammenfassung |
We report on the unexpected detection of considerable structure in high
latitude thermospheric densities, as derived from an accelerometer onboard
the CHAMP satellite. The width of the structures, which can either be maxima
or minima, varies between a few hundred km and 2000 km. The amplitudes of
these density extrema can reach 50% of ambient. Maxima cluster around
75° (N and S), while minima are found closer to the poles. In a magnetic
latitude-magnetic local time frame the maxima are found mainly around the
cusp region. Overall, the observed structures somewhat resemble so-called
density cells previously found in model calculations. However the models
generate their cells around 140–300 km altitude and show little, if any
remnant at 400 km or above. This has to be contrasted with the fact that the
CHAMP observations were obtained near 430 km altitude. We have explored
Joule heating as a possible mechanism for the generation of the structures,
at least in density enhancement regions, using Hall currents measured on
CHAMP and simultaneous incoherent scatter measurements with EISCAT. However,
the electric fields were usually quite small during the period of
observation, making the quest for an explanation for the structures all the
more challenging.
Keywords. Meteorology and atmospheric dynamics (Thermospheric
dynamics) – Magnetospheric physics (Polar cap
phenomena) – Atmospheric composition and structure (Pressure,
density, and temperature) |
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