Global gyrokinetic stability of pressure-gradient-driven electromagnetic modes in tokamaks with regions of low shear

Tokamaks with large pressure gradients (αmax) formed in regions of weak magnetic shear are shown to be susceptible to novel, low-n, global, kinetic, electromagnetic modes with a toroidal mode number n in the range 2≤n≤12. For a weakly varying monotonic safety factor profile q with its minimum qmin>1 on the magnetic axis and αmax near qmin, new, global kinetic infernal modes with a strong mode rotation ωr and a finite growth rate γ< vertical bar ωr vertical bar are found. For equilibria with reverse shear where qmin is off axis and αmax near qmin, the existence of an unstable low-n global branch of Alfven ion temperature gradient modes is revealed with an oscillatory γ as a function of n. The addition of trapped electron dynamics is shown to be further destabilizing