Finite-β ion mixing mode in sheared magnetic geometry

The theory of ion temperature gradient driven instabilities (ion mixing modes) is presented for finite-β plasmas in sheared magnetic fields. Specifically the strong instability of long wavelength modes (perpendicular wavelengths larger than the ion gyral radius) is considered and it is analytically shown that these modes cannot be stabilized at reasonable values of β, where shear Alfvén dynamics are the dominant electromagnetic effect. The strong instability, with ‖ω/k∥vTi‖>1, persists in the regime me/mi<β<1.