The flute instability of a plasma driven by the electrostatic high-frequency eigenmodes

The stability problem of a plasma immersed in a high frequency field is studied on a simple model. It is supposed that the fundamental h. f. electrostatic eigenmode having the frequency lower than the electron cyclotron frequency is excited in a slab of a cold collisionless magnetized plasma with the symmetrical density profile. The stability of low-frequency short-wavelength flute perturbations is investigated. Averaging over fast time oscillations and by using the WKB method to cope with the problem of the space inhomogeneity we have obtained the expression for the electron drift velocity. Making use of this velocity and quasineutrality condition we have derived the local dispersion equation. It is shown how the growth rate depends on the amplitude of the h. f. mode and that h. f. eigenmodes having the frequency close to the plasma frequency in the middle of the slab can partially stabilize the gravitational flute instability.The authors wish to thank Dr. R.Klíma for helpful discussion.