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| Titel |
A case study of gravity wave dissipation in the polar MLT region using sodium LIDAR and radar data |
| VerfasserIn |
T. Takahashi, S. Nozawa, M. Tsutsumi, C. Hall, S. Suzuki, T. T. Tsuda, T. D. Kawahara, N. Saito, S. Oyama, S. Wada, T. Kawabata, H. Fujiwara, A. Brekke, A. Manson, C. Meek, R. Fujii |
| 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 ; 32, no. 10 ; Nr. 32, no. 10 (2014-10-07), S.1195-1205 |
| Datensatznummer |
250121114
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| Publikation (Nr.) |
 copernicus.org/angeo-32-1195-2014.pdf |
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| Zusammenfassung |
| This paper is primarily concerned with an event observed from 16:30 to
24:30 UT on 29 October 2010 during a very geomagnetically quiet interval
(Kp ≤ 1). The sodium LIDAR observations conducted at Tromsø, Norway
(69.6° N, 19.2° E) captured a clearly discernible gravity
wave (GW) signature. Derived vertical and horizontal wavelengths, maximum
amplitude, apparent and intrinsic period, and horizontal phase velocity were
about ~ 11.9 km, ~ 1.38 × 103 km, ~ 15 K, 4 h,
~ 7.7 h, and ~ 96 m s−1, respectively, between a height of 80 and 95 km. Of particular
interest is a temporal development of the uppermost altitude that the GW
reached. The GW disappeared around 95 km height between 16:30 and 21:00 UT,
while after 21:00 UT the GW appeared to propagate to higher altitudes (above
100 km). We have evaluated three mechanisms (critical-level filtering,
convective and dynamic instabilities) for dissipations using data obtained by
the sodium LIDAR and a meteor radar. It is found that critical-level
filtering did not occur, and the convective and dynamic instabilities
occurred on some occasions. MF radar echo power showed significant
enhancements between 18:30 and 21:00 UT, and an overturning feature of the
sodium mixing ratio was observed between 18:30 and 21:20 UT above about
95 km. From these results, we have concluded that the GW was dissipated by wave breaking and instabilities before 21:00 UT. We have also
investigated the difference of the background atmosphere for the two
intervals and would suggest that a probable cause of the change in the GW
propagation was due to the difference in the temperature gradient of the
background atmosphere above 94 km. |
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