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| Titel |
Long-term changes in thermospheric composition inferred from a spectral analysis of ionospheric F-region data |
| VerfasserIn |
C. J. Scott, R. Stamper, H. Rishbeth |
| 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 ; 32, no. 2 ; Nr. 32, no. 2 (2014-02-17), S.113-119 |
| Datensatznummer |
250121025
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| Publikation (Nr.) |
 copernicus.org/angeo-32-113-2014.pdf |
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| Zusammenfassung |
| A study of ionospheric data recorded at Slough/Chilton, UK, from 1935 to
2012, has revealed long-term changes in the relative strength of the annual
and semi-annual variability in the ionospheric F2 layer critical frequencies.
Comparing these results with data from the southern hemisphere station at
Stanley in the Falkland Islands between 1945 and 2012 reveals a trend that
appears to be anti-correlated with that at Chilton. The behaviour of
foF2 is a function of thermospheric composition and so we argue that
the observed long-term changes are driven by composition change. The
ionospheric trends share some of their larger features with the trend in the
variability of the aa geomagnetic index. Changes to the semi-annual/annual
ratio in the Slough/Chilton and Stanley data may therefore be attributable to
the variability in geomagnetic activity which controls the average
latitudinal extent of the auroral ovals and subsequent thermospheric
circulation patterns. Changes in ionospheric composition or thermospheric
wind patterns are known to influence the height of the F2 layer at a given
location. Long-term changes to the height of the F2 layer have been used to
infer an ionospheric response to greenhouse warming. We suggest that our
observations may influence such measurements and since the results appear to
be dependent on geomagnetic longitude, this could explain why the long-term
drifts observed in F2 layer height differ between locations. |
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