Intermittency in fluid turbulence can be emphasized through the analysis of Probability Distribution Functions (PDF) for velocity fluctuations, which display a strong non‐gaussian behavior at small scales. Castaing et al. (1990) have introduced the idea that this behavior can be represented, in the framework of a multiplicative cascade model, by a convolution of gaussians whose variances is distributed according to a log‐normal distribution. In this letter we have tried to test this conjecture on the MHD solar wind turbulence by performing a fit of the PDF of the bulk speed and magnetic field intensity fluctuations calculated in the solar wind, with the model. This fit allows us to calculate a parameter λ² depending on the scale, which represents the width of the log‐normal distribution of the variances of the gaussians. The physical implications of the obtained values of the parameter as well as of its scaling law are finally discussed.

Using a multifractal approach, based on “singularity analysis,” we investigate the scaling properties of the auroral electrojet index (AE) time series. The existence of a multifractal structure in the AE time series is the signature of the occurrence of “intermittence,” which can be interpreted as an indication of turbulence in magnetospheric dynamics. Furthermore, a simple model, the P-model (a two-scale Cantor set), is shown in order to investigate the underlying multiplicative nature of the signal. This set displays many of the multifractal properties of the AE signal.