A study on chaotic behaviour of equatorial/low latitude ionosphere over Indian subcontinent, using GPS-TEC time series

Unnikrishnan, K. P.; Ravindran, Sudha

doi:10.1016/j.jastp.2010.07.003

Cited by 27 publications

(21 citation statements)

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“…Ionosphere structure and peak densities in the ionosphere vary greatly with time (sunspot cycle, seasonally and diurnally), with geographical location (polar, auroral zones, mild latitudes, and equatorial regions), and with certain solarrelated ionospheric disturbances. During and following a geomagnetic storm, the ionospheric changes around the globe as observed from the ground site can appear chaotic (FullerRowell et al, 1994;Cosolini and Chang, 2001;Unnikrishnan and Ravindran, 2010). The presence of chaos is indicated by the positive values of the Lyapunov exponent found in all the computations for all the TEC values obtained for the selected days for all the measuring stations used in this work.…”

Section: Discussionmentioning

confidence: 69%

“…These changes can indicate some level of determinism in the ionosphere. The rise and fall in the computed values of Tsallis entropy daily five window intervals indicate the interplay between stochasticity and determinism (Unnikrishnan and Ravindran, 2010). The Tsallis entropy was able to show the deterministic behavior of the ionosphere considering its response during storm periods compared with other relatively quiet periods, as the rapid drop in values of Tsallis entropy during storms show that there is a transition from higher complexity during quiet periods to lower complexity during storms.…”

Section: Discussionmentioning

confidence: 90%

“…1 show a pattern similar to the detrended TEC plot. It has been established that TEC does not decrease totally throughout the night as expected normally through the simple theory of the fact that TEC builds up during the day, but it shows some anomalous enhancements and variations and this can occur under a wide range of geophysical conditions (Balan and Rao, 1987;Balan et al, 1991;Unnikrishnan and Ravindran, 2010).…”

Section: Discussionmentioning

confidence: 92%

“…The Theiler window was chosen to be approximately equal to the product of m and τ . A similar approach to the computation of correlation dimensions was used by Unnikrishnan and Ravindran (2010) to determine the correlation dimension of detrended TEC data for some stations in India, which lies within the equatorial region, like Nigeria. The correlation dimension for data taken for the quietest day of October 2011 and the most disturbed day of October 2011 from Lagos GPS TEC measuring station are represented by Fig.…”

Section: Correlation Dimensionmentioning

confidence: 99%

“…Also, Unnikrishnan et al (2006a, b) analyzed the deterministic chaos at mid-latitude. Also, Unnikrishnan (2010); Unnikrishnan and Ravindran (2010) analyzed some TEC data from some Indian low-latitude stations for quiet and major storm periods, and found in their results the presence of chaos, which was indicated by a positive Lyapunov exponent and also showed storm periods with lower values compared with quiet periods.…”

Section: Introductionmentioning

confidence: 99%

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The comparative study of chaoticity and dynamical complexity of the low-latitude ionosphere, over Nigeria, during quiet and disturbed days

Ogunsua

Laoye

Fuwape

et al. 2014

Nonlin. Processes Geophys.

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Abstract. The deterministic chaotic behavior and dynamical complexity of the space plasma dynamical system over Nigeria are analyzed in this study and characterized. The study was carried out using GPS (Global Positioning System) TEC (Total Electron Content) time series, measured in the year 2011 at three GPS receiver stations within Nigeria, which lies within the equatorial ionization anomaly region. The TEC time series for the five quietest and five most disturbed days of each month of the year were selected for the study. The nonlinear aspect of the TEC time series was 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 like Lyapunov exponents, correlation dimension and also Tsallis entropy for the measurement of dynamical complexity. The observations made show positive Lyapunov exponents (LE) for both quiet and disturbed days, which indicates chaoticity, and for different days the chaoticity of the ionosphere exhibits no definite pattern for either quiet or disturbed days. However, values of LE were lower for the storm period compared with its nearest relative quiet periods for all the stations. The monthly averages of LE and entropy also show no definite pattern for the month of the year. The values of the correlation dimension computed range from 2.8 to 3.5, with the lowest values recorded at the storm period of October 2011. The surrogate data test shows a significance of difference greater than 2 for all the quantifiers. The entropy values remain relatively close, with slight changes in these values during storm periods. The values of Tsallis entropy show similar variation patterns to those of Lyapunov exponents, with a lot of agreement in their comparison, with all computed values of Lyapunov exponents correlating with values of Tsallis entropy within the range of 0.79 to 0.81. These results show that both quantifiers can be used together as indices in the study of the variation of the dynamical complexity of the ionosphere. The results also show a strong play between determinism and stochasticity. The behavior of the ionosphere during these storm and quiet periods for the seasons of the year are discussed based on the results obtained from the chaotic quantifiers.

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Section: Discussionmentioning

confidence: 69%

Section: Discussionmentioning

confidence: 90%

Section: Discussionmentioning

confidence: 92%

Section: Correlation Dimensionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

The comparative study of chaoticity and dynamical complexity of the low-latitude ionosphere, over Nigeria, during quiet and disturbed days

Ogunsua

Laoye

Fuwape

et al. 2014

Nonlin. Processes Geophys.

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How does solar eclipse influence the complex behavior of midlatitude ionosphere? Two case studies

Unnikrishnan

Richards

2014

JGR Space Physics

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This paper investigates the influence of two solar eclipses on the ionosphere complexity measures: Tsallis entropy, Rényi entropy, Hurst exponent, beta exponent, and fractal dimension. The study used GPS TEC measured at three locations in Japan during the solar eclipses of 22 July 2009 and 21 May 2012. This is the first effort to compare the complexity measures by comparing TEC time series of the eclipse day with those from the day before and the day after the eclipse. It was found from analysis of the TEC observations that there were no abnormal variations of the complexity parameters from their expected values for either eclipse. Model calculations also show that TEC deviations during the eclipses are small.

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Linear scaling and periodicity on the measures of global and local scale complexities of total electron content dynamics

Kumar

Eapen²

2013

JGR Space Physics

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[1] In this paper, we compare the local and global dynamics of total electron content (TEC) by analyzing Lyapunov exponents and correlation dimensions. The internal structure of the underlying system is studied using TEC data from the solar minimum years [2007][2008]. The mutual information, false nearest neighbors, and space-time separation of both local and global snapshots are estimated and analyzed. It indicates that although the internal dynamics changes with season, the pattern of variation over the seasons remains identical for both the years, suggesting that the characteristics of these changes might be predictable. We report the evidence of a linear scaling with slope 0.00187 and a periodicity with period of 1 year on measures of global and local scale complexities of TEC dynamics. This behavior appears to be a universal phenomenon unaffected by change of cycles and amount of information influencing the complexity, since they are almost constant over the 2 years. The global Lyapunov exponent increases linearly over a year, whereas the local Lyapunov exponent increases up to the middle of the year, attains greatest local complexity, and then decreases. This suggests that local prediction is more reliable than the global one. The estimated invariants characterize the complex dynamics as it evolve from local time to global time and also provide information to the system's heterogeneity. The features such as presence of multiple attractors, linear scaling, and nearly regular seasonal periodicity may have practical consequences and could yield insights into the internal dynamics of TEC and the modeling of its variations.Citation: Kumar, C. V. A., and S. Eapen (2013), Linear scaling and periodicity on the measures of global and local scale complexities of total electron content dynamics,

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A study on chaotic behaviour of equatorial/low latitude ionosphere over Indian subcontinent, using GPS-TEC time series

Cited by 27 publications

References 50 publications

The comparative study of chaoticity and dynamical complexity of the low-latitude ionosphere, over Nigeria, during quiet and disturbed days

The comparative study of chaoticity and dynamical complexity of the low-latitude ionosphere, over Nigeria, during quiet and disturbed days

How does solar eclipse influence the complex behavior of midlatitude ionosphere? Two case studies

Linear scaling and periodicity on the measures of global and local scale complexities of total electron content dynamics

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