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Article Dans Une Revue Annales Geophysicae Année : 2007

Climatic trends in E-region critical frequency and virtual height above Tromsø (70° N, 10° E)

C. M. Hall
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P. S. Cannon
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Résumé

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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Dates et versions

hal-00318408 , version 1 (18-06-2008)

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  • HAL Id : hal-00318408 , version 1

Citer

C. M. Hall, A. Brekke, P. S. Cannon. Climatic trends in E-region critical frequency and virtual height above Tromsø (70° N, 10° E). Annales Geophysicae, 2007, 25 (11), pp.2351-2357. ⟨hal-00318408⟩

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