Numerical Analysis of Current-Driven Drift-Wave Instability in a Finite- β Plasma

Stability of the collisionless drift wave localized to the rational surface is studied numerically. Both the current and the finite- β effects are taken into account. The results confirm the previous analytical and/or numerical results concerning the stableness in the currentless case, instability driven by the current and its finite- β stabilitzation in the short wavelength region. In addition, a strong resonant coupling of the drift wave to the Alfvén wave is found to occur due to the combined effect of the current and the finite- β value, resulting a destabilizing effect in the long wavelength region. The critical electron drift velocity for the onset of the instability is calculated. The result shows a substantial reduction of the critical velocity by the finite- β effect.