ABSTRACT
This chapter describes nonlinear wave phenomena in a fluid model for the plasma dynamics in homogeneous, isotropic plasmas (in reality this means unmagnetized plasmas). It considers weakly nonlinear Langmuir waves and also ion acoustic waves. Finite amplitude Langmuir waves have two sorts of contributions to their nonlinear evolution. The chapter discusses the nonlinearity arising from a finite displacement of the pendulum mass. An additional effect can arise in the case that the displacement of the pendulum somehow affects the length of the supporting string. An equation for the Langmuir waves is derived in terms of a yet unspecified perturbation of the bulk plasma density, and it remains to find a mechanism by which the Langmuir waves can induce such a perturbation, i.e., modify the index of refraction of the plasma in which they propagate.
