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" (${k_{\theta }}^{\prime }\cong k_{\theta }$) and "distant" (${k_{\theta }}^{\prime }{a}_s\cong \frac{1}{k_{\theta }{a}_s}$) interactions. The spectral index $n=4\mathrm{}$ of the high-mode-number tail is independent of the excitation mechanism.