Universal instability and ion temperature gradient instability in sheared magnetic fields

Abstract

From analytical solutions of the slab eigenmode equation for drift waves, the normal mode growth rates are obtained in uniform magnetic fields. In a sheared magnetic field, it is shown that approximately three times the shear of Pearlstein and Berk is required for stability, when we retain only the usual Landau resonance term. The principal part of plasma dispersion function stabilizes the universal instability considerably, in zero-order approximation. However, on the ion temperature gradient instability, its effect is negligible.