The Dispersion Equation of MGD Waves for non-stationary Plasmas
  The dispersion equation of MGD plasma waves measured in a reference frame with a relative speed from that where they are generated is derived. The analysis leads further from what is known for waves produced in stationary plasmas in the presence of an imposed magnetic field, and includes terms containing space gradients in the density and speed values in the continuity and momentum equations of the plasma. The dispersion equation that is derived leads to an Alfven wave and magnetogasdynamics wave modes whose distribution with respect the direction of the imposed magnetic field varies with the relative speed of the reference frame. For the particular case in which the speed of the reference frame is zero the dispersion equation of the magnetogasdynamic waves reduces to what is known for stationary plasmas. More complicated waves with different distribution modes with respect to the magnetic field direction are implied from the more general four-order dispersion equation that is derived. A particular case is presented for a non-zero speed value of the reference frame, but the derivation and analysis of the corresponding solutions will be discussed in a forthcoming report. 
H. P\'erez-de-Tejada and Eric G\'omez-G\'omez
physics.space-ph