Landau Damping of Ion Acoustic Waves in a Uniform Magnetic Field

Abstract

Landau damping of ion acoustic waves in a relatively weak magnetic field has been experimentally studied. Both artificially created contaminant Landau damping and electron Landau damping have been examined for arbitrary propagation angles from 0° (parallel)to 90° (perpendicular). It has been found that for perpendicular propagation, the contaminant Landau damping disappears for wave frequencies ω such that ω < ωciHe. Also, for ω > 4ωciHe, the damping without magnetic field has been completely recovered. Electron Landau damping is observable only when the waves propagate almost perpendicularly to the magnetic field. The wave frequency has been kept much higher than the major ion cyclotron frequency so that the ion acoustic waves can propagate in any direction.