COLLISIONAL DAMPING OF PLASMA OSCILLATIONS

The linearized kinetic equation with a uniform external magnetic field is solved for the perturbed electron distribution function. The collision term is assumed small, but otherwise is arbitrary. Using this solution, the general dispersion relation for electron waves is derived. One mode, longitudinal plasma oscillations along the magnetic field, is worked out in detail with the Landau (Fokker-Planck) collision term. An equivalent moment equation approach is also used, and it is found that the divergence of the heat flow tensor must be retained in the third-moment equation in order to obtain the correct first-order thermal correction to the damping rate. Both methods yield ωI = -1/2ωp(2/π)1/2(lnΛ/Λ)[1 - (2 - 4 √2/5)k2λD2]. This damping rate decreases as k increases, and disagrees with earlier results based on the Landau equation. It appears that these previous treatments have not included the complete thermal correction.