Unstable ion sound in plasmas with drifting electrons
Center for Plasma Astrophysics, Celestijnenlaan 200B, 3001 Leuven, Belgium
Corresponding author: a Jovo.Vranjes@wis.kuleuven.be
Revised: 23 May 2006
Published online: 30 June 2006
The properties of a weakly ionized plasma with a high concentration of flowing neutrals are discussed as well as the excitation of ion sound oscillations propagating obliquely to the magnetic field lines. The model used in the present study includes collisions of plasma species with neutrals in the limit when electrons are magnetized but ions are not. The electron collision frequency is higher than the shifted wave frequency, which allows for the fluid description of the electrons. The ion-neutral collision frequency remains arbitrary and, therefore, the ion species is described by a collisional Boltzman kinetic equation. The electron drift in the perpendicular direction results in the instability of accidentally excited ion sound oscillations, which turn out to be highly unstable for practically all physically acceptable values of the electron drift. In addition, the presence of a population of hotter electrons is shown to reduce the perpendicular electron drift and to increase the instability threshold.
PACS: 52.35.Fp – Electrostatic waves and oscillations (e.g., ion-acoustic waves) / 52.25.Ya – Neutrals in plasmas / 52.25.Dg – Plasma kinetic equations
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2006