Gaussian Mixtures in Solar Wind Plasma Turbulence

Based on previous analyses of data from a fleet of space exploration missions, we argue that plasma fluctuations in the turbulent solar wind are consistently described by normal variance mixtures on a broad range of scales encompassing the inertial and kinetic scales. In the inertial range, the normal variance mixture distributions are derived from conditioning the Elsasser field increments either on fluctuations of the energy transfer rate or on fluctuations of the singularity strength. The two kinds of description can be linked to each other via bridging relations. An exact analytical expression for the even-order structure functions is obtained from a normal inverse Gaussian fit, accurate from inertial to dissipative scales in the plasma. The self-similar kappa distributions describing the kinetic scales result from an inverse chi(2) distribution of the variance in the Gaussian mixture model.