Stochastic particle transport by fluctuating electric fields

Abstract

Particle transport in one and two dimensions due to random electric fields is studied using a simple model based on a Fokker-Planck description. The fields are assumed to be specified by a given spectrum, E( k), which determines the relative importance of each field component to the transport, and their effect is concentrated to spatial regions the size of the correlation length. Particle trajectories are determined, and by performing appropriate averaging we compute transport coefficients in velocity space, which can then be used to compute macroscopic transport coefficients. This procedure can give the stopping power of a medium to a test particle dominated by electric fluctuations rather than collisions. The particular system considered is an unmagnetized plasma but the same model can be applied to other media where the fluctuating electric fields are characterized by a typical length such as the dimensions of granules or the pore widths.