Kinetic Description of Plasmas

Abstract

In the previous chapters, the description of the plasma state was refined step by step. In the single-particle model, we were interested in the motion of individual particles in typical magnetic field configurations, but the interaction between the particles and the modification of the fields by the presence and motion of charged particles was neglected. In the fluid model, we had considered the average behavior of particles filling a small volume of space. In this approximation, only moments of a shifted Maxwell distribution, like mean flow velocity or gas temperature, were retained, but, by combining with Maxwell’s equations, the model became self-consistent. The fluid model goes beyond the single-particle model in that pressure effects are now included. This fluid model, and its formulation in terms of MHD-equations, became capable to describe the combined macroscopic motion of plasma and magnetic field lines. A first attempt to deal with non-Maxwellian velocity distributions was the introduction of a beam-plasma system, which generates self-excited electrostatic waves near the electron plasma frequency.