ABSTRACT
In this chapter, the authors took the simplest possible version of the two-fluid model for describing waves in homogeneous and isotropic plasmas. The plasma is described as two fluids, electrons and ions, solely interacting by the electric and magnetic fields they set up. The simplest analysis assumes that the ions as well as the electron temperature vanish. Evidently, this assumption can never be exactly fulfilled, but the results obtained by it have nonetheless proved most valuable, in particular by offering a convenient classification of electromagnetic waves in plasmas. The basic equations are the simple fluid equations for plasma continuity and the momentum equations, together with Maxwell’s equations. For the longitudinal waves, the authors find that the plasma current and the Maxwell displacement current exactly cancel, and there are no magnetic perturbations associated with these waves. They are consequently termed electrostatic, since the electric fields can be derived from Poisson’s equation, just as in classical electrostatics.
