Waves in inhomogeneous moving media with application to the solar wind

Consider a MHD system composed of waves and a slowly varying background fluid through which they propagate. Following the work of Dewar and Bretherton, a variational approach is used to derive a complete set of equations for the interacting wave-background system. The resulting fluid equations for the background state include terms which represent the momentum and energy flux of the waves. These equations are general in that they are valid for any MHD wave mode, and consistent in that both the total momentum and total energy of the system are conserved. The effect of the waves on the mean state of the fluid is represented by a wave stress tensor. The wave stress tensor and the terms due to waves in both the momentum and energy equations are calculated for various special cases which are likely to be relevant to the solar atmosphere. To complete the system of equations, I derive the dispersion relation and the equation of conservation of wave action, which governs the wave amplitude