Eigenfrequencies of Ion-Acoustic Waves in the Presence of Electron-Ion Collisions

Frequencies and damping rate of ion-acoustic waves in the presence of electron-ion collisions are computed by reducing the linearized electron Fokker-Planck equation and cold-ion fluid equations to an eigenvalue equation via moment expansion of the perturbation of electron distribution function. As electrons becomes less collisional, a great number of Sonine modes are needed for convergence to a desired accuracy in the calculation, which may be ascribed to the neglected electron-electron collisions.