Intermittency and self-similarity in ‘natural parameters’ in solar wind turbulence

Abstract

This chapter reviews a generic probability density functions (PDF) rescaling method to fluctuations in solar wind bulk plasma parameters. The solar wind provides a natural laboratory for observations of magnetohydrodynamic (MHD) turbulence over extended temporal scales. Self-similarity has been identified in the probability density functions of fluctuations in certain solar wind bulk plasma parameters as seen by the WIND spacecraft. Whereas, the fluctuations of speed v and IMF magnitude B are multi-fractal, it is found that the fluctuations in the ion density ρ, energy densities B2and ρv2 along with MHD-approximated Poynting flux vB2are self-similar on the timescales up to ∼26 hours. The chapter argues that these are ‘natural parameters' in which the solar wind measurements are casted that are taken in an Eulerian frame of reference. The intermittency of the system is then expressed in these parameters through the non-Gaussian nature of the single curve that describes the fluctuations PDF up to this timescale.