Niveau: Supérieur, Doctorat, Bac+8
Chapter 2 KINETIC THEORY 2.1 Distribution Functions A plasma is an ensemble of particles electrons e, ions i and neutrals n with di?erent positions r and velocities v which move under the influence of external forces (electromagnetic fields, gravity) and internal collision processes (ionization, Coulomb, charge exchange etc.) However, what we observe is some “average” macroscopic plasma parameters such as j - current density, ne - electron density, P - pressure, Ti - ion temperature etc. These parameters are macrsocopic averages over the distribution of particle velocities and/or positions. In this lecture we • Introduce the concept of the distribution function f?(r,v, t) for a given plasma species; • Derive the force balance equation (Boltzmann equation) that drives the temporal evolution of f?(r,v, t); • Show that low order velocity moments of f?(r,v, t) give various important macroscopic parameters; • Consider the role of collision processes in coupling the charged and neutral speicies dynamics in a plasma and • Show that low order velocity moments of the Boltzmann equation give “fluid” equations for the evolution of the macroscopic quantities.
- phase space
- density
- phase space flow
- ∂f ∂t
- changes negligibly
- independent coordinates
- equation describes
- change
- boltzmann equation
- dt