Characteristic Oscillations in Sheet Plasmas

Electrostatic eigenmodes in a sheet plasma of thickness of the order of the ion Larmor radius ρ i have been studied numerically. The frequency range considered is in the ion cyclotron regime, where the ion Bernstein mode and the electrostatic ion cyclotron mode can be excited. The method is based on an integral equation in the wavenumber space derived from the Vlasov-Poisson system of equations and on the direct computation of the integral equation. Eigenfrequencies and eigenfunctions are studied systematically by varying the plasma thickness, the plasma density, the electron-to-ion temperature ratio and the parallel wavenumber. Unique features for the case of the ideal sheet plasma, where the plasma thickness is equal to ρ i are disclosed and explained by a simple physical model, whereas for a plasma of thickness 5ρ i the eigenfrequencies are nearly equal to those of a uniform plasma. Results are compared with experimental results.