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| Titel |
Climatological features of electron density in the polar ionosphere from long-term observations of EISCAT/ESR radar |
| VerfasserIn |
H. T. Cai, S. Y. Ma, Y. Fan, Y. C. Liu, 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 ; 25, no. 12 ; Nr. 25, no. 12 (2008-01-02), S.2561-2569 |
| Datensatznummer |
250015962
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| Publikation (Nr.) |
 copernicus.org/angeo-25-2561-2007.pdf |
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| Zusammenfassung |
| In this paper, climatological features of the polar F2-region
electron density (Ne) are investigated by means of statistical
analysis using long-term observations from the European Incoherent
Scatter UHF radar (called EISCAT in the following) and the EISCAT
Svalbard radar (ESR) during periods of quiet to moderate geomagnetic
activity. Field-aligned measurements by the EISCAT and ESR radars
operating in CP-1 and CP-2 modes are used in this study, covering
the years 1988–1999 for EISCAT and 1999–2003 for ESR. The data are
sorted by season (equinox, summer and winter) and solar cycle phase
(maximum, minimum, rising and falling). Some novel and interesting
results are presented as follows: (1) The well-known winter anomaly
is evident during the solar maximum at EISCAT, but it dies out at
the latitude of the ESR; (2) The daytime peaks of Ne at EISCAT
for all seasons during solar maximum lag about 1–2 h behind
those at ESR, with altitudes about 10–30 km lower. (3) In addition
to the daytime peak, it is revealed that there is another peak just
before magnetic midnight at ESR around solar maximum, especially in
winter and at equinox. The day-time ionization peak around magnetic
noon observed by ESR can be attributed to soft particle
precipitation in the cusp region, whereas the pre-midnight Ne
maximum seems likely to be closely related to substorm events which
frequently break out during that time sector, in particular for the
winter case. (4) Semiannual variations are found at EISCAT during
solar minimum and the falling phase of the solar cycle; at the rising
phase, however, the EISCAT observations show no obvious seasonal
variations. |
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