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| Titel |
Equatorial ionospheric response to the 10.7 cm radio flux over two sunspot cycles (1969-1991) |
| VerfasserIn |
L. A. Hajkowicz |
| 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 ; 14, no. 7 ; Nr. 14, no. 7, S.725-732 |
| Datensatznummer |
250012354
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| Publikation (Nr.) |
 copernicus.org/angeo-14-725-1996.pdf |
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| Zusammenfassung |
| It is evident that fluctuations in a standard
ionospheric parameter, the minimum (virtual) height (h´F)
of the equatorial F-region in the African (Ouagadougou), Asian (Manila) and
American (Huancayo) longitudinal sectors, closely resemble changes in solar
activity as deduced from the 10.7 cm solar flux index (S), over two solar
cycles (1969–91). The monthly median hourly value of h´F,
particularly in the post-sunset period (18–20 LT), are positively correlated
with the monthly average S. The value of h´F
can be deduced from an empirical formula: h´F=0.68S+218.3,
with the correlation coefficient (r) between h´F
and S being 0.78. The diurnal distribution of r during daytime
(06–14 LT) was radically different for the African and Asian longitudinal
sectors during 1980-1991, with the most pronounced difference in the post-noon
period (12–14 LT) when the correlation coefficients r for the Asian and
African sectors are 0.8 and 0.2, respectively. Thus, the daytime F-region in the
African sector responded far less to changes in solar activity than the Asian
F-region during this cycle. This longitudinal anomaly was however absent in the
preceding cycle (1969–1979) when the African and Asian sectors were both
characterised by low daytime and pronounced post-sunset correlation coefficient r.
The American sector appears to have a high correlation coefficient r in
daytime increasing to a small maximum in the post-sunset interval. The
post-sunset enhancement in r is a characteristic feature for equatorial
stations only (corrected geomagnetic latitude <10°). |
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