Non‐Gaussian distribution function of AE‐index fluctuations: Evidence for time intermittency

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Abstract
The probability distribution functions (Pdfs) of the AE‐index fluctuations at different time scales have been investigated using a time series covering a period from January 01, 1978 to December 31, 1985. The Pdfs are always non Gaussian for time scales in the range 1–120 min both in quiet and disturbed periods. The scale dependence of the Pdfs indicates that AE‐index is not characterized by a global time self‐similarity, indicating that an intermittency phenomenon characterizes both phases. The results on Pdfs are compared with functional form, proposed by Castaing et al. [1990], to characterize intermittency phenomena in ordinary turbulent fluid flows. Moreover the relevance of these observations to the understanding of the magnetospheric dynamical configuration is pointed out.