The numerical solution of a high-n electrostatic ballooning mode is obtained. Correct forms of electron and ion responses to the wave are retained. Instabilities which arise because of toroidal effects are found. Dependence on the aspect ratio, magnetic shear, wavelength, electron-ion-temperature ratio, and the electron temperature gradient is also studied. The growth rate γ is large and satisfies the relation ω<γ∼ω*. Depending on the parameters, the real frequency ω changes sign. The drift mode, which has been found to be stable in a slab plasma, persists in the toroidal plasma, almost always remaining stable. The density fluctuations in tokamaks, which have been observed when the microwave scattering method is used, can be qualitatively explained by the theory of the electrostatic ballooning mode.
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