[1] In this paper we report the evidence of a low-dimensional chaos in a set of data observed outside laboratories. The dynamic behavior of the time series of the fluctuations of the total electron content (TEC) measured at Goose Bay, which is a high-latitude station, is analyzed in detail using the tools of nonlinear dynamics. The low-dimensional character of the dynamics is evident from the estimated value of the fraction of false neighbors for various dimensions and the correlation dimension. The deterministic nature of the dynamics is investigated using recurrence plots and spatiotemporal entropy. The chaotic nature of the underlying dynamics of the fluctuations of TEC is shown by the power spectrum indicating exponential decay and the calculated positive value of Lyapunov exponent. This is also supported by the results of the comparison of the chaotic characteristics of the time series of variations of TEC with the pseudochaotic characteristic of the colored noise time series. The results of the tests based on the prediction error and the time reversal asymmetry statistic reject the hypothesis that TEC belongs to the family of linear stochastic signals. The nonlinear non-Gaussian nature of the oscillations of variations of TEC is further investigated by the surrogate data test based on several geometrical and dynamical characteristics of the variations of TEC such as mutual information, the fraction of the false nearest neighbours, the local slopes of the correlation sums, the curves giving Lyapunov exponents, and finally, the value of Lyapunov exponents. The results of this analysis show that low-dimensional chaotic dynamics could be a possible and fruitful concept which can be utilized to study the disturbance in the ionosphere as in the case of magnetospheric dynamics. We feel that the dynamical invariants like Lyapunov exponents and correlation dimension can describe the disturbance in the variations of TEC and thus the disturbance in the ionosphere. Hence the techniques of nonlinear and chaos theory and the measure of the dynamical invariants could be used for the characterization and thus for the modeling of variations of the total electron content.

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