High-Frequency Conductivity of a Plasma with Fluctuations

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Abstract
The induced current density of a fully ionized, stationary, and uniform plasma linear in the externally applied, high-frequency electric field is calculated. In the calculation two approximations are made: neglect of the spatial dependence of the external field and neglect of the mode-coupling terms which do not significantly contribute to damping of the waves. For large ion-to-electron mass ratios, the Ohmic current can be expressed as a simple function of the density fluctuations of the electrons and those of the ions. Results previously obtained for a quiescent plasma can easily be recovered by using the expressions for these fluctuations one obtains from the velocity distribution functions in the random phase approximation. Each of the three different types of enhanced fluctuations, corresponding to the ion-acoustic, the ion plasma, and the electron plasma waves, respectively, is found to have a different effect on the resistivity. The range of frequencies of the external field in which the effect of fluctuations is important, the sign of the additional resistivity due to fluctuations, and a quantitative estimate of this resistivity in some special cases are discussed.