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| Titel |
A climatology of the F-layer equivalent winds derived from ionosonde measurements over two decades along the 120°-150°E sector |
| VerfasserIn |
X. Luan, L. Liu, W. Wan, J. Lei, T. Yu |
| 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 ; 22, no. 8 ; Nr. 22, no. 8 (2004-09-07), S.2785-2796 |
| Datensatznummer |
250014965
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| Publikation (Nr.) |
 copernicus.org/angeo-22-2785-2004.pdf |
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| Zusammenfassung |
| The vertical equivalent winds (VEWs) at the F-layer
are analyzed along the 120°-150°E longitude sector with an
emphasis on their latitudinal dependence. The VEWs are derived from the
monthly median data of fourteen ionosonde stations over two decades. The
results show that the VEWs have considerable dependences on the magnetic
latitude with an approximate symmetry about the magnetic equator. They are
mostly controlled by the electric field drifts in the magnetic equatorial
region, and shift to be mostly contributed by neutral winds at mid-latitudes.
The relative contribution of the two dynamic factors is regulated by the
magnetic dip in addition to their own magnitudes. The VEWs generally have opposite
directions and different magnitudes between lower and higher latitudes. At
solar minimum, the magnitudes of VEWs are only between -20 and 20m/s at lower
latitudes, while at higher latitudes they tend to increase with latitudes,
typically having magnitudes between 20-40m/s. At solar maximum, the VEWs
are reduced by about 10-20m/s in magnitudes during some local times at
higher latitudes. A tidal analysis reveals that the relative importance of
major tidal components is also different between lower and higher latitudes.
The VEWs also depend on local time, season and solar activity. At higher
latitudes, the nighttime VEWs have larger magnitude during post-midnight
hours and so do the daytime ones before midday. The VEWs tend to have an
inverse relationship with solar activity not only at night, but also by day,
which is different from the meridional winds predicted by the HWM93 model.
The latitudinal dependence of VEWs has two prevailing trends: one is a
maximum at the highest latitudes (as far as the latitudes concerned in the
present work); the other is a mid-latitude maximum. These two latitudinal
trends are mostly dependent on season, while they depend relatively weakly on
local time and solar activity. The latitudinal gradients of VEWs also show a
tendency of a mid-latitude maximum, except that there are much stronger
latitudinal gradients at southern higher mid-latitudes in some seasons. The
gradients during daytime are much smaller at solar maximum than minimum,
whereas they are generally comparable at night under both solar activity
levels. |
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