Marginal stability of ion-acoustic waves in a weakly collisional two-temperature plasma without a current

In this Brief Report, 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 (Tₑ₀/Tᵢ₀{)}1/2(5/16(2{m}i/me)1/2 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.