Ballooning Modes in the Systems Stabilized by Divertors

MHD stability of a plasma in systems with closed magnetic field lines and open systems containing the nonparaxial stabilizing cells with large field lines curvature, in particular, divertors is analyzed. It is shown that population of particles trapped in such cells has a stabilizing effect not only on flute modes, but also on ballooning modes that determine the limit. At kinetic description that accounts for different effect of trapped and passing particles on perturbations, limit permitted by stability may be much greater then it follows from MHD model.