Numerical analyses using a gyro-fluid model have been performed to investigate the finite-Larmor-radius (FLR) effect on ion-temperature-gradient (ITG) instability in cylindrical plasmas. A spectrum code with Fourier-Bessel expansion has been developed for the analysis of global mode structures. The analytical expression of the η (ratio between the density and temperature gradient lengths) threshold value for linear ITG instability has been obtained from the local dispersion relation, whose dependency on the ion temperature comes from the FLR effect. Dependency of the threshold by the global analysis is reproduced by the local analysis with appropriate selection of the perpendicular wavenumber. Break of the Boltzmann relation by the FLR effect is not strong as to generate another unstable branch of the ITG mode.
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