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| Titel |
Mean thermospheric winds observed from Halley, Antarctica |
| VerfasserIn |
R. I. Crickmore |
| 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 ; 12, no. 10/11 ; Nr. 12, no. 10/11, S.1101-1113 |
| Datensatznummer |
250010349
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| Publikation (Nr.) |
 copernicus.org/angeo-12-1101-1994.pdf |
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| Zusammenfassung |
| Thermospheric winds on a total of 237 nights
have been studied for the effects due to geomagnetic activity, solar flux, and
season. The observations have been made from 1988 to 1992 by a Fabry-Perot
interferometer (FPI) operating at Halley (75.5°S, 26.6°W),
Antarctica. This is the first statistical study of thermospheric winds near the
southern auroral zone. The main factor affecting the wind velocities is the
geomagnetic activity. Increases in activity cause an increase in the maximum
equatorward wind, and cause the zonal wind in the evening to become more
westward. Smaller changes in the mean wind occur with variations in season and
solar flux. The small variation with solar flux is more akin to the situation
found at mid-latitudes than at high latitudes. Since the geomagnetic latitude of
Halley is only 61°, it suggests that the variability of the wind
with solar flux may depend more on geomagnetic than geographic latitude. These
observations are in good agreement with the empirical Horizontal Wind Model
(HWM90). However, comparisons with predictions of the Vector Spherical Harmonic
Model (VSH) show that for low geomagnetic activity the predicted phases of the
two components of the wind closely resemble the observations but the modelled
amplitudes are too small by a factor of two. At high geomagnetic activity the
major differences are that modelled zonal velocity is too westward in the
evening and too eastward after 04 UT. The modelled ion densities at the F-region
peak are a factor of up to 9 too large, whilst the predicted mean value and
diurnal variation of the altitude of the peak are significantly lower than those
observed. It is suggested that these differences result from the ion loss rate
being too low, and an inaccurate model of the magnetic field. |
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