A two-component transport model for solar wind fluctuations: Waves plus quasi-2D turbulence

Abstract

We present a model for the transport of solar wind fluctuations, based on the assumption that they can be well-represented using two distinct components: a quasi-2D turbulence piece and a wave-like piece. For each component, coupled transport equations for its energy, cross helicity, and characteristic lengthscale(s) are derived, along with an equation for the proton temperature. This energy-containing “two-component” model includes the effects of solar wind expansion and advection, driving by stream shear and pickup ions, and nonlinear cascades. Nonlinear effects are modeled using a recently developed one-point phenomenology for such a two-component model of homogeneous MHD turbulence [1]. Heating due to these nonlinear effects is included in the temperature equation. Numerical solutions are discussed and compared with observations