MHD compressive turbulence in the solar wind and the nearly incompressible approach

Abstract

At MHD scales density fluctuation in the solar wind generally have a relative amplitude less than 0.1. The nearly incompressible MHD theory would seem then appropriate to describe a major part of the compressive turbulence at these scales. As a test of the theory, we focus on the scaling properties of density fluctuations with turbulent Mach numbers and on the level of correlation between density and temperature fluctuations. Our findings do not appear in favour of an extended applicability of the nearly incompressible theory to MHD compressive turbulence in the solar wind.