FLUCTUATIONS OF A CHARGED BROWNIAN PARTICLE IN A PLASMA

The system-size expansion technique, is used to study the fluctuations both near and far from equilibrium of a charged Brownian particle in a two-component plasma. The method is based on the master equation that governs the conditional probability density function of the velocity. This method yields a macroscopic equation for the slowing down of the heavy charged particle; and in the linear noise approximation, equations for the mean and variance of the fluctuations around the macroscopic behavior are found and a fluctuation-dissipation theorem is demonstrated. The velocity-velocity correlation function and the diffusion coefficient of these particles are also determined in this approximation, both near and far from equilibrium. Numerical examples are used to illustrate the results. The generalization to multispecies plasma is apparent. © 1990 The American Physical Society.