MHD Turbulence: Generalized Formulation and Extension to Compressible Cases

A general framework that incorporates the Iroshnikov-Kraichnan (IK) and Goldreich-Sridhar (GS) phenomenologies of MHD turbulence is developed. This affords a clarification of the regimes of validity of the IK and GS models. This formulation is generalized further to include compressibility effects.