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| Titel |
Climatic trends in E-region critical frequency and virtual height above Tromsø (70° N, 10° E) |
| VerfasserIn |
C. M. Hall, A. Brekke, P. S. Cannon |
| 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. 11 ; Nr. 25, no. 11 (2007-11-29), S.2351-2357 |
| Datensatznummer |
250015945
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| Publikation (Nr.) |
 copernicus.org/angeo-25-2351-2007.pdf |
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| Zusammenfassung |
| We have examined the long time series of observations of E-region virtual
height (1948–2006) and critical frequency (1935-2006) hitherto made by the
Tromsø ionosonde at 70° N, 19° E. Combining a simplistic trend
analysis with a rigorous treatment of errors we identify a negative trend in
critical frequency. While a similar analysis of the virtual height h'E also
suggests a negative trend, a closer examination reveals a possible weak
positive trend prior to ~1975 and a strong negative trend from ~1975 to present. These two metrics of essentially the same feature of the
ionosphere do not exhibit the same signature since critical frequency is
controlled by photochemistry within the E-layer while height is controlled
by pressure level. We further find that the trend in critical frequency is a
daylight/summer phenomenon, no significant trend being evident in the winter
subset of the data. On the other hand, the trends in virtual height are
independent of season/daylight. |
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