Physics of Plasmas

This chapter is intended to provide a brief introduction in plasma physics, including common definitions, basic properties and typical processes found in plasmas. These include the basic physical laws governing plasmas, electrostatics of plasma, quasi-neutrality of the plasma, plasma oscillations, the Saha ionization equation, the Hall effect, forces on an ion stream in electric and magnetic fields, the probabilistic nature of plasma velocities, plasma velocities in an electric field, collisions between charged particles and Debye shielding, the collective behaviour of plasma particles, motion of a single charged particle in an electromagnetic field, plasma instabilities and drifts, magnetic mirrors and plasma confinement by magnetic fields. These and other related concepts are inherent in contemporary plasma-based spacecraft thrusters and thus provide a foundation for the methods and concepts that will be presented in the following chapters. The reader is only assumed to be familiar with basic electrodynamics and fluid mechanics. The chapter also discusses the modelling of plasmas as a fluid, the magneto-gas dynamic equations governing such fluid flows as well as a number other related concepts associated with such flows.