Drift-Wave Spectra Obtained from the Theory of Nonlinear Ion-Landau Damping in Sheared Magnetic Fields

The local character, in poloidal mode-number space, of the resonant nonlinear interaction of drift waves with ions in a sheared magnetic field permits an analytical determination of the spectrum. Important processes underlying the stabilization are energy cascade and transfer, respectively, in "close" (k_θ^'k_θ) and "distant" (k_θ^'aₛ1k_θaₛ) interactions. The spectral index $n=4$ of the high-mode-number tail is independent of the excitation mechanism.