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| Titel |
The transient variation in the complexes of the low-latitude ionosphere within the equatorial ionization anomaly region of Nigeria |
| VerfasserIn |
A. B. Rabiu, B. O. Ogunsua, I. A. Fuwape, J. A. Laoye |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1023-5809
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| Digitales Dokument |
URL |
| Erschienen |
In: Nonlinear Processes in Geophysics ; 22, no. 5 ; Nr. 22, no. 5 (2015-09-11), S.527-543 |
| Datensatznummer |
250120998
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| Publikation (Nr.) |
 copernicus.org/npg-22-527-2015.pdf |
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| Zusammenfassung |
| The quest to find an index for proper characterization and description of the
dynamical response of the ionosphere to external influences and its various
internal irregularities has led to the study of the day-to-day variations of
the chaoticity and dynamical complexity of the ionosphere. This study was
conducted using Global Positioning System (GPS) total electron content (TEC)
time series, measured in the year 2011, from five GPS receiver stations in
Nigeria, which lies within the equatorial ionization anomaly region. The
non-linear aspects of the TEC time series were obtained by detrending the
data. The detrended TEC time series were subjected to various analyses to
obtain the phase space reconstruction and to compute the chaotic quantifiers,
which are Lyapunov exponents LE, correlation dimension, and Tsallis entropy,
for the study of dynamical complexity. Considering all the days of the year,
the daily/transient variations show no definite pattern for each month, but
day-to-day values of Lyapunov exponents for the entire year show a wavelike
semiannual variation pattern with lower values around March, April, September
and October. This can be seen from the correlation dimension with values
between 2.7 and 3.2, with lower values occurring mostly during storm periods,
demonstrating a phase transition from higher dimension during the quiet
periods to lower dimension during storms for most of the stations. The values
of Tsallis entropy show a similar variation pattern to that of the Lyapunov
exponent, with both quantifiers correlating within the range of 0.79 to 0.82.
These results show that both quantifiers can be further used together as
indices in the study of the variations of the dynamical complexity of the
ionosphere. The presence of chaos and high variations in the dynamical
complexity, even in quiet periods in the ionosphere, may be due to the
internal dynamics and inherent irregularities of the ionosphere which exhibit
non-linear properties. However, this inherent dynamics may be complicated by
external factors like geomagnetic storms. This may be the main reason for the
drop in the values of the Lyapunov exponent and Tsallis entropy during
storms. The dynamical behaviour of the ionosphere throughout the year, as
described by these quantifiers, was discussed in this work. |
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