Properties of kinetic Alfvén waves: A comparison of fluid models with kinetic theory

Although the solar wind, as a collisionless plasma, is properly described by the kinetic Maxwell-Vlasov description, it can be argued that much of our understanding of the solar wind is based on a fluid description of magnetohydrodynamics that derives from interpretation of observational data together with numerical modeling. In recent years, there has been significant interest in better understanding the importance of kinetic effects, i.e., the differences between kinetic and fluid descriptions. Here we concentrate on the physical properties of oblique kinetic Alfven waves (KAWs) that appear to be a key ingredient in the solar wind turbulence cascade. We use three different fluid models with various degrees of complexity and calculate the polarization and magnetic compressibility of KAWs (propagation angle θ = 88°), which we compare to solutions derived from linear kinetic theory. We explore a wide range of possible proton plasma β = [0.1, 10.0] and a wide range of length scales k⊥rL = [0.001, 10.0], whe...