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| Titel |
A comparative study on chaoticity of equatorial/low latitude ionosphere over Indian subcontinent during geomagnetically quiet and disturbed periods |
| VerfasserIn |
K. Unnikrishnan |
| 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 ; 17, no. 6 ; Nr. 17, no. 6 (2010-12-15), S.765-776 |
| Datensatznummer |
250013763
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| Publikation (Nr.) |
 copernicus.org/npg-17-765-2010.pdf |
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| Zusammenfassung |
| In the present study, the latitudinal aspect of chaotic behaviour of
ionosphere during quiet and storm periods are analyzed and compared by using
GPS TEC time series measured at equatorial trough, crest and outside crest
stations over Indian subcontinent, by employing the chaotic quantifiers like
Lyapunov exponent (LE), correlation dimension (CD), entropy and nonlinear
prediction error (NPE). It is observed that the values of LE are low for
storm periods compared to those of quiet periods for all the stations
considered here. The lowest value of LE is observed at the trough station,
Agatti (2.38° N, Geomagnetically), and highest at crest station,
Mumbai (10.09° N, Geomagnetically) for both quiet and storm periods.
The values of correlation dimension computed for TEC time series are in the
range 2.23–2.74 for quiet period, which indicate that equatorial ionosphere
may be described with three variables during quiet period. But the crest
station Mumbai shows a higher value of CD (3.373) during storm time, which
asserts that four variables are necessary to describe the system during storm
period. The values of non linear prediction error (NPE) are lower for Agatti
(2.38° N, Geomagnetically) and Jodhpur (18.3° N,
Geomagnetically), during storm period, compared to those of quiet period,
mainly because of the predominance of non linear aspects during storm periods
The surrogate data test is carried out and on the basis of the significance
of difference of the original data and surrogates for various aspects, the
surrogate data test rejects the null hypothesis that the time series of TEC
during storm and quiet times represent a linear stochastic process. It is
also observed that using state space model, detrended TEC can be predicted,
which reasonably reproduces the observed data. Based on the values of the
above quantifiers, the features of chaotic behaviour of equatorial trough
crest and outside the crest regions of ionosphere during geomagnetically
quiet and disturbed periods are briefly discussed. |
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