Damping of ion-acoustic waves in the presence of electron-ion collisions

The properties of ion-acoustic waves in a plasma are investigated by analytically solving the electron Fokker-Planck (FP) and cold-ion fluid equations for arbitrary electron-ion (e-i) collision strength. This is achieved by developing a reduced form of the FP equation with a generalized collision frequency. It is demonstrated that the effective wave damping can be treated as a combination of collisional and collisionless mechanisms. Contrary to several previous reports, weak e-i collisions are shown to increase the damping rate above the collisionless electron Landau limit.