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| Titel |
Equinoctial transitions in the ionosphere and thermosphere |
| VerfasserIn |
A. V. Mikhailov, K. Schlegel |
| 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 ; 19, no. 7 ; Nr. 19, no. 7, S.783-796 |
| Datensatznummer |
250014289
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| Publikation (Nr.) |
 copernicus.org/angeo-19-783-2001.pdf |
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| Zusammenfassung |
Equinoctial summer/winter
transitions in the parameters of the F2-region are analyzed using ground-based
ionosonde and incoherent scatter observations. Average transition from one type
of diurnal NmF2 variation to another takes 20–25 days, but cases of very fast
(6–10 days) transitions are observed as well. Strong day-time NmF2 deviations
of both signs from the monthly median, not related to geomagnetic activity, are
revealed for the transition periods. Both longitudinal and latitudinal
variations take place for the amplitude of such quiet time NmF2 deviations. The
summer-type diurnal NmF2 variation during the transition period is
characterized by decreased atomic oxygen concentration [O] and a small
equatorward thermospheric wind compared to winter-type days with strong
poleward wind and increased [O]. Molecular N2 and O2
concentrations remain practically unchanged in such day-to-day transitions. The
main cause of the F2-layer variations during the transition periods is the
change of atomic oxygen abundance in the thermosphere related to changes of
global thermospheric circulation. A possible relationship with an equinoctial
transition of atomic oxygen at the E-region heights is discussed.
Key words. Atmospheric composition
and structure (thermosphere – composition and chemistry) – Ionosphere
(ionosphere- atmosphere interactions; ionospheric disturbances) |
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