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

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

 

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Title: Climatic trends in E-region critical frequency and virtual height above Tromsø (70 degrees N, 10 degrees E)
Author: Cannon, P. S.; Hall, Chris; Brekke, Asgeir
Date: 29-Nov-2007
Type: Journal article; Tidsskriftartikkel; Peer reviewed
Abstract: 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 degrees N, 19 degrees 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.
Description: This is the publishers version/PDF (published in Annales Geophysicae, an open access journal of the European Geosciences Union)
Publisher: Copernicus Publications on behalf of the European Geosciences Union
Citation: Annales Geophysicae, 25, 2351–2357, 2007
URI: http://hdl.handle.net/10037/2385


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