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Abstract
AbstractIn a recent study, mid-latitude ionospheric parameters were compared with solar activity; it was suggested that the relationship between these, earlier assumed stable, might be changing with time (Lastovicka, 2019). Here, the information is extended to higher latitude (69.6°N, 19.2E) and further back in time. For the ionospheric F-region (viz. the critical frequency, FoF2) the same behaviour is seen with a change-point around 1996. For the ionospheric E-region (viz. the critical frequency, foE), change-points are less obvious than in the mid-latitude study, presumably owing to the observation site lying under the auroral oval.
Highlights
With an increasingly long time-series of parameters from the upper atmosphere, it is becoming viable to investigate climatology
Upper atmosphere trends or change can reflect corresponding ones in the troposphere (Hall et al, 2007; Roble & Dickinson, 1989), but at an altitude not directly influenced by local short-term effects
The solar dependence is demonstrated by a linear regression including the 95% confidence limits (Working & Hotelling, 1929): 2.1 Æ 0.1 MHz/100 sunspots, for foF2 and a high degree of confidence; 0.2 Æ 0.1 MHz/100 sunspots, for foE and a considerably lower degree of confidence. The latter, foE, demonstrates the much weaker dependence compared with foF2 as shown by Lastovicka (2019), but considerably more variable, reflecting the mechanisms in the auroral zone
Summary
With an increasingly long time-series of parameters from the upper atmosphere, it is becoming viable to investigate climatology. Upper atmosphere trends or change can reflect corresponding ones in the troposphere (Hall et al, 2007; Roble & Dickinson, 1989), but at an altitude not directly influenced by local short-term effects. One endeavours to establish the mechanisms responsible for observed trends, one contender being solar forcing: the focus of this study and that of Lastovicka (2019). Once this effect has been removed, it may be possible to identify others, including anthropogenic causes, if any
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