Simulation study of Bernstein modes

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Abstract
The properties of Bernstein modes were investigated through computer simulations using two‐dimensional and two‐and‐one‐half‐dimensional (i.e., two spatial and three velocity coordinates) electrostatic models with fixed magnetic field. The measured discrete spectrum was found to agree with the linear dispersion relation for these modes. The quasi‐periodic phenomenon of early phase‐mixing damping and later recurrence, predicted by Baldwin and Rowlands, was observed. For large wavenumber k⊥, the initial damping rate is the same as that for Landau damping in an unmagnetized plasma; for small k⊥, however, it is much stronger. The recurrence peaks slowly damp in time at a rate proportional to k2⊥D, where D is the measured cross‐field particle diffusion coefficient which is dominated by convective transport. Finally, splitting of the main spectral peaks and the appearance of subpeaks at half‐integral multiples of the cyclotron frequency are observed and may be explained by nonlinear mode coupling.