The friction and diffusion coefficients of the Fokker-Planck equation in a plasma. II

Abstract

In two recent papers a method of calculation of the coefficients of the Fokker-Planck equa­tion which includes in a proper way correlation effects between distant particles has been expounded. In this paper the theory is extended to include a proper treatment of close binary encounters. It is also shown that the higher-order terms of the Fokker-Planck equation may be summed to produce a Boltzmann-like contribution to the collision term. Finally, it is shown that in the approximation in which only ‘dominant’ terms are retained, the theory reproduces a number of well-known formulae, including the ordinary Boltzmann collision term, but now with a suitable cut-off built in.