A probabilistic approach to heterogeneity in space plasmas: the case of magnetic field intensity in solar wind

Abstract

Since the early 90s it was shown that Probability Distribution Functions (PDFs) of small scale differences (fluctuations) of several quantities in space plasmas display significant departures from Gaussianity. The non-Gaussian shape of PDFs was ascribed to intermittency and discussed in the framework of intermittent MHD turbulence. Here, we put the attention to the PDF of magnetic field intensity instead of its differences showing how the PDF of such quantity in a quiet solar wind can be related with the occurrence of heterogeneity. In detail, we derive the shape of the PDFs by simple statistical considerations based on the concept of <i>subordination</i> in probability theory. An interpretation and a discussion in terms of existing coherent magnetic structures in a mechanical near-equilibrium state are also presented.