Marginal Stability of Ion-Acoustic Waves in a Weakly Collisional Two-Temperature Plasma without a Current

摘要

This report presents two important results for a weakly collisional, current-free, two-temperature electron-ion plasma: (1) that e-i collisions have an undamping effect on ion acoustic waves, and (2) that, for appropriate values of the plasma parameters, ion-acoustic waves become marginally stable. The results are based on the closed form solution for the dielectric function for the linearized Balescu-Lenard-Poisson kinetic equations. The weakly collisional ordering is necessary to obtain an iterative solution for the collisional dielectric function, imposes two independent restrictions on the parameters that characterize the plasma. The linearized Balescu-Lenard-Poisson equations are solved in the weakly collisional limit to show that ion-acoustic waves in a current-free plasma, which are Landau-damped in the absence of collisions, can become marginally stable due to the undamping effect of electron-ion (e-i) collisions. For sq rt.(T sub e0/T sub i0) << (5/16) sq rt.(m sub i/m sub e), the e-i collisional undamping effect dominates the i-i, e-e, and i-e collisional effects, and marginal stability occurs when the collisional undamping rate balances the electron and ion Landau damping rates. Keywords: Ion acoustic waves; Two temperature plasma. (JHD)