ABSTRACT
In plasma fluid theory, plasma is characterized by a few local parameters—such as the particle density, the kinetic temperature, and the flow velocity—the time evolutions of which are determined by means of fluid equations. Fluid variables are relatively easy to measure in experiments, whereas, in most cases, it is extraordinarily difficult to measure a distribution function accurately. Boltzmann's collision operator for a neutral gas considers only binary collisions, and is, therefore, bilinear in the distribution functions of the two colliding species. There are two basic types of fluid closure schemes. In truncation schemes, higher order moments of the distribution function are assumed to vanish, or are prescribed in terms of lower moments. Asymptotic schemes, on the other hand, depend on the rigorous exploitation of some small parameter. In particular, the cold-plasma equations provide a good description of the propagation of electromagnetic waves through plasmas.
