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| Titel |
Tidal variations in the high-latitude E- and F-region observed by EISCAT |
| VerfasserIn |
Klemens Hocke |
| 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 ; 14, no. 2 ; Nr. 14, no. 2, S.201-210 |
| Datensatznummer |
250012169
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| Publikation (Nr.) |
 copernicus.org/angeo-14-201-1996.pdf |
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| Zusammenfassung |
| During the MLTCS (Mesosphere-Lower
Thermosphere Coupling Study) campaign the EISCAT UHF radar was continuously
operated over 7 days (30 July–5 August 1992) in the CP-1 mode. The long time
series obtained of the fundamental ionospheric parameters field-aligned ion
velocity (Vi), ion and electron temperature (T and Te),
and electron density (Ne) are useful in investigating tidal
variations in the E- and F-region since the geomagnetic activity was
particularly low during the time of measurement. Maximum entropy spectra of the
parameters were calculated for the relatively quiet interval from 1 August to 4
August 1992 and indicated dominant variations with harmonics of 24 hours. In the
electron density spectrum especially, harmonics up to the sixth order (4-h
period) are clearly visible. The phase and amplitude height profiles (100–450
km) of the diurnal, semidiurnal, and terdiurnal variations were determined by
Fourier transform for a 24-h data set beginning at 12:00 UT on 3 August 1992
when the contaminating influences of electric fields were negligible. The tidal
variations of the ion temperatures are compared with the corresponding
variations of the neutral temperature predicted by the MSISE-90 model. A
remarkable result is the dominance of terdiurnal temperature oscillations at
E-region heights on 3–4 August 1992, while the measured diurnal and semidiurnal
variations were negligible. The finding was confirmed by the analysis of further
EISCAT data (2–3 August 1989, 2–3 July 1990, 31 March–1 April 1992) which also
showed a dominant terdiurnal temperature tide in the E-region. This is different
from numerous observations of tides in the E-region at mid-latitudes where the
diurnal and especially the semidiurnal temperature oscillations were dominant. |
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