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| Titel |
On the possible role of cusp/cleft precipitation in the formation of polar-cap patches |
| VerfasserIn |
I. K. Walker, J. Moen, L. Kersley, D. A. Lorentzen |
| 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 ; 17, no. 10 ; Nr. 17, no. 10, S.1298-1305 |
| Datensatznummer |
250013825
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| Publikation (Nr.) |
 copernicus.org/angeo-17-1298-1999.pdf |
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| Zusammenfassung |
The work describes experimental observations
of enhancements in the electron density of the ionospheric F-region created by
cusp/cleft particle precipitation at the dayside entry to the polar-cap
convection flow. Measurements by meridian scanning photometer and all-sky camera
of optical red-line emissions from aurora are used to identify latitudinally
narrow bands of soft-particle precipitation responsible for structured
enhancements in electron density determined from images obtained by radio
tomography. Two examples are discussed in which the electron density features
with size scales and magnitudes commensurate with those of patches are shown to
be formed by precipitation at the entry region to the anti-sunward flow. In one
case the spectrum of the incoming particles results in ionisation being created,
for the most part below 250 km, so that the patch will persist only for minutes
after convecting away from the auroral source region. However in a second
example, at a time when the plasma density of the solar wind was particularly
high, a substantial part of the particle-induced enhancement formed above 250
km. It is suggested that, with the reduced recombination loss in the upper
F-region, this structure will retain form as a patch during passage in the
anti-sunward flow across the polar cap.
Key words. Ionosphere (ionospheric irregularities;
particle precipitation; polar ionosphere) |
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