On apparent temperature in low-frequency Alfvenic turbulence

Low-frequency, parallel propagating Alfvenic turbulence in collisionless plasmas is theoretically studied. Alfvenic turbulence is derived as an equilibrium state (Beltrami field) in the magnetohydrodynamic equations with the pressure anisotropy and multi-species of ions. It is shown that the conservation of the total apparent temperature corresponds to the Bernoulli law. A simple model of the radially expanding solar wind including Alfvenic turbulence is also discussed. The conversion of the wave energy in the apparent temperature into the real temperature is facilitated with increasing radial distance. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4747499]