NON-GAUSSIAN DISTRIBUTION FUNCTION OF AE-INDEX FLUCTUATIONS - EVIDENCE FOR TIME INTERMITTENCY

The probability distribution functions (Pdfs) of the AE-index fluctuat ions at different time scales have been investigated using a time seri es covering a period from January 01, 1978 to December 31, 1985. The P dfs are always non Gaussian for time scales in the range 1-120 min bot h in quiet and disturbed periods. The scale dependence of the Pdfs ind icates that AE-index is not characterized by a global time self-simila rity, indicating that an intermittency phenomenon characterizes both p hases. 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 obser vations to the understanding of the magnetospheric dynamical configura tion is pointed out.