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| Titel |
The polar cliff in the morning sector of the ionosphere |
| VerfasserIn |
G. W. Prölss |
| 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 ; 31, no. 5 ; Nr. 31, no. 5 (2013-05-24), S.957-966 |
| Datensatznummer |
250019043
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| Publikation (Nr.) |
 copernicus.org/angeo-31-957-2013.pdf |
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| Zusammenfassung |
| By "polar cliff" we mean the steep increase in the
ionization density observed in the morning sector of the polar ionosphere. Here
the properties of this remarkable feature are investigated. The data set
consists of electron density and temperature measurements obtained by the
Dynamics Explorer 2 satellite. Only data recorded in the Northern Hemisphere winter
are considered (solar zenith angle ≥ 90°). We find that for moderately disturbed conditions,
the foot of the polar cliff is located below 60° invariant latitude. Here,
within about 4°, the density increases by a factor of 4, on average. The
actual location of the polar cliff depends primarily on the level of
geomagnetic activity, its associated density increase on geographic longitude
and altitude. As to the longitudinal variations, they are attributed to
asymmetries in the background ionization density at middle latitudes. Using a
superposed epoch type of averaging procedure, mean latitudinal profiles of the
polar cliff and the associated electron temperature changes are derived. Since
these differ significantly from those derived for the afternoon/evening sector,
we conclude that the subauroral ionospheric trough does not extend into the
morning sector. As to the origin of the polar cliff in the morning sector,
local auroral particle precipitation should play only a secondary role. |
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