Most of the matter in the Universe is in the plasma state. A plasma will be defined and the concepts of quasi-neutrality and Debye distance introduced. The subject has its historical roots in gas discharge, astrophysics and ionospheric physics. Key theoretical concepts were developed in the context of those subjects. However, only in the last two decades, under the pressures of the controlled thermonuclear and space exploration programmes, have these concepts been tested experimentally. The theory of collisions in plasma has special features owing to the Coulomb nature of the interaction. Magnetized plasma is a medium in which a rich variety of small signal waves can propagate. Charged particle—wave interactions lead to collisionless (Landau) damping and growth mechanisms. Finally, nonlinear phenomena in plasma can and do change its transport properties by orders of magnitude. Our lack of detailed understanding of these nonlinear phenomena applies equally to natural plasmas and to plasmas in both inertially and magnetically confined fusion systems. This feature provides the challenge and the fascination of high temperature plasma physics.
Experimental investigation on large amplitude standing wave induced in closed tubes with varying cross section