BALLOONING INSTABILITY IN HIGH \beta TOKAMAK

In this paper we show that \Delta′_B is negative over parts of the second region, and that plasmas are stable to \Delta′_B -driven resistive modes for realistic equilibria in which characteristics of finite-\beta configurations are retained. We have found that ideal instability is very sensitive to the ratio T=r\Delta″/\Delta′ in the second region. In comparison with previous works. results obtained by present authors show that the shift gradient \Delta′ has a significant stabilizing effect on the second stable boundary, and this effect increases as the shear s becomes larger.