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| Titel |
Variations in the altitude of the F2 peak associated with trough-formation processes |
| VerfasserIn |
R. I. Crickmore, B. Jenkins, G. J. Bailey |
| 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. 6 ; Nr. 14, no. 6, S.628-636 |
| Datensatznummer |
250012322
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| Publikation (Nr.) |
 copernicus.org/angeo-14-628-1996.pdf |
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| Zusammenfassung |
| A novel approach is described which can help
to determine, from ground-based data, which of the possible production
mechanisms for the mid-latitude F-region ionospheric trough is dominant during a
particular event. This approach involves numerically modelling the possible
causal mechanisms of the mid-latitude trough to see how each will affect the
altitude of the F2-layer electron-concentration peak (hmF2), and then comparing
these predictions with the observed variation of hmF2 during trough formation.
The modelling work predicts that, if the neutral-wind velocity does not vary,
hmF2 will remain almost constant if the trough is formed via stagnation, but
will rise if it is formed as a result of high ion velocities or neutral
upwelling. Observations made at Halley (76°S, 27°W, L=4.2), Antarctica,
show that most frequently the only changes in hmF2 during trough formation are
those expected due to variations in the neutral wind, which suggests that
stagnation is the most common production mechanism. During the most
geomagnetically active night studied, on which Ap varied between 18 and 32,
there was a rise in hmF2 that cannot be explained by changes in the neutral
wind. On this night the plasma also decayed faster, and the poleward edge of the
trough was seen earlier than on other nights. These differences, together with
the fact that the ion velocities remained relatively low, suggest the trough was
caused by a change in neutral composition, possibly advected into the observing
area. |
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