TIME-DEPENDENT STATISTICAL PROPERTIES OF THE ELECTRIC MICROFIELD SEEN BY A NEUTRAL RADIATOR

We study the dynamical properties of the electric microfield at a fixed neutral point immersed in a one-component plasma. We introduce an effective-field approach for describing the correlations between the microfield densities at two different times. In this approach, the essential features of the dynamics of the charges that produce the microfield are incorporated via suitable choices of the effective field. We present two versions of the theory which, in the static limits, reduce to the mean-force and adjustable-parameter exponential (APEX) approximations for the equilibrium distribution of the microfield. Both versions rely on a few ingredients determined through existent theories for the dynamics and the statics of the particles. The comparison to the molecular-dynamics data shows that the dynamical extension of APEX is the most reliable theory. The predictions of the Brissaud and Frisch model [J. Quant. Spectrosc. Radiat. Transfer 11, 1767 (1971)] for the microfield dynamics are also tested against the simulation results. This model turns out to be rather reasonable. However, it is not as accurate as APEX, and it misses oscillatory behaviors (originating from the plasmon modes) which, on the contrary, are qualitatively reproduced by the latter theory.