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| Titel |
The transient variation of 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 |
2198-5634
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| Digitales Dokument |
URL |
| Erschienen |
In: Nonlinear Processes in Geophysics Discussions ; 1, no. 2 ; Nr. 1, no. 2 (2014-12-05), S.1855-1903 |
| Datensatznummer |
250115137
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| Publikation (Nr.) |
 copernicus.org/npgd-1-1855-2014.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 5 GPS receiver stations in Nigeria
which lies within the Equatorial Ionization Anomaly region. The
nonlinear aspect of the TEC time series were obtained by detrending
the data. The detrended TEC time series were subjected to various
analyses for phase space reconstruction and to obtain the values of
chaotic quantifiers which are Lyapunov exponents LE, correlation
dimension, and Tsallis entropy for the study of dynamical
complexity. The results show positive Lyapunov exponents for all
days which indicate chaoticity of the ionosphere with no definite
pattern for both quiet and disturbed days. However values of LE
were lower for the storm period compared to its nearest relative
quiet periods for all the stations. 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 exponent for the entire
year show a wavelike semiannual variation pattern with lower values
around March, April, September and October, a change in pattern
which demonstrates the self-organized critical phenomenon of the
system. 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 similar
variation pattern with that of Lyapunov exponent with a lot of
agreement in their comparison, with all computed values of Lyapunov
exponent correlating with values of Tsallis entropy within the range
of 0.79 to 0.82. These results show that Lyapunov quantifiers can be
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 at 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 Lyapunov exponent and Tsallis
entropy during storms. The results also show a strong interplay
between determinism and stochasticity, as the ionosphere shows its
response to changes in solar activities and in its internal
dynamics. The dynamical behavior of the ionosphere throughout the
year as described by these quantifiers, were discussed in this work. |
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