Stabilization mechanism of the feedback instability with height-resolved ionosphere and Alfven resonator models

Eigenvalue analysis of feedback instability in a magnetosphere-ionosphere (M-I) coupling model has been extended to study the stabilization mechanism of high-frequency shear Alfven modes by introducing both an inhomogeneous conductivity profile and an ionospheric Alfven resonator. Stabilization of high-frequency modes is attributed to change of the effective impedance due to the non-uniform ionospheric conductivity along the field line rather than the collision-induced flow shear, while low-frequency modes relevant to auroral arc excitation remain unstable. An effective impedance model incorporating the inhomogeneous conductivity profile is also developed as an extension of the height-integrated ionosphere model.