Kinetic ballooning mode under steep gradient: High order eigenstates and mode structure parity transition

Abstract

The existence of kinetic ballooning mode (KBM) high order (non-ground) eigenstates for tokamak plasmas with a steep gradient is demonstrated via gyrokinetic electromagnetic eigenvalue solutions, which reveals that eigenmode parity transition is an intrinsic property of electromagnetic plasmas. The eigenstates with quantum number l = 0 for ground state and l = 1, 2, 3…for non-ground states are found to coexist and the most unstable one can be the high order states (l ≠ 0). The conventional KBM is the l = 0 state. It is shown that the l = 1 KBM has the same mode structure parity as the micro-tearing mode (MTM). In contrast to the MTM, the l = 1 KBM can be driven by the pressure gradient even without collisions and the electron temperature gradient. The relevance between various eigenstates of the KBM under a steep gradient and edge plasma physics is discussed.