Multiple-gap theory of toroidal Alfvén waves with kinetic effects

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Abstract
The stability of kinetic toroidal Alfvén waves with multigap coupling is analyzed by using the two-dimensional ballooning transform. An alternate convergence scheme, based on the smallness of the inverse aspect ratio, is devised. The resulting wave functions are oscillatory and do not balloon in contrast to the wave functions of conventional ballooning theory. It is shown that the single-gap theory is a special, weak shear (s→0) limit of the formalism. Analytical and numerical results for the two fundamental branches, the ideal toroidal Alfvén eigenmode (TAE), and the kinetic toroidal Alfvén eigenmode (KTAE), are presented and discussed.