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| Titel |
Comparison of equatorial GPS-TEC observations over an African station and an American station during the minimum and ascending phases of solar cycle 24 |
| VerfasserIn |
A. O. Akala, G. K. Seemala, P. H. Doherty, C. E. Valladares, C. S. Carrano, J. Espinoza, S. Oluyo |
| 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 ; 31, no. 11 ; Nr. 31, no. 11 (2013-11-22), S.2085-2096 |
| Datensatznummer |
250086153
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| Publikation (Nr.) |
 copernicus.org/angeo-31-2085-2013.pdf |
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| Zusammenfassung |
| GPS-TEC data were observed at the same local time at two equatorial stations
on both longitudes: Lagos (6.52° N, 3.4° E,
3.04° S magnetic latitude), Nigeria; and Pucallpa
(8.38° S, 74.57° W, 4.25° N magnetic latitude),
Peru during the minimum (2009, 2010) and ascending (2011) phases of solar
cycle 24. These data were grouped into daily, seasonal and solar activity
sets. The day-to-day variations in vertical TEC (VTEC) recorded the maximum
during 14:00–16:00 LT and minimum during 04:00–06:00 LT at both
longitudes. Seasonally, during solar minimum, maximum VTEC values were
observed during March equinox and minimum during solstices. However, during
the ascending phase of the solar activity, the maximum values were recorded
during the December solstice and minimum during the June solstice. VTEC also
increased with solar activity at both longitudes. On longitude by longitude
comparison, the African GPS station generally recorded higher VTEC values
than the American GPS station. Furthermore, harmonic analysis technique was
used to extract the annual and semi-annual components of the amplitudes of
the TEC series at both stations. The semi-annual variations dominated the TEC
series over the African equatorial station, while the annual variations
dominated those over the American equatorial station. The GPS-TEC-derived
averages for non-storm days were compared with the corresponding values
derived by the IRI-2007 with the NeQuick topside option. The NeQuick option
of IRI-2007 showed better performance at the American sector than the African
sector, but generally underestimating TEC during the early morning hours at
both longitudes. |
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