Current-driven drift wave instability in a sheared magnetic field

In a sheared magnetic field, the eigenfunction of the drift wave is asymmetrized by a current along B0. Taking into account this asymmetrizing effect, a stability condition for the current-driven drift mode in a sheared field is derived. For magnetic shear generated by the plasma current, a low limit on βe—the ratio of plasma pressure to magnetic pressure—is required for the stability of a plasma with given density and gradient.