NIFS-360

FULL TEXT (PDF, 1114 KB)


Author(s):

K. Itoh, S.-I. Itoh, M. Yagi and A. Fukuyama

Title:

Dynamic Structure in Self-Sustained Turbulence

Date of publication:

June 1995

Key words:

Self-sustained turbulence, ballooning mode, interchange mode, anomalous transport, radial electric field gradient, magnetic shear, subcritical turbulence

Abstract:

Dynamical equation for the self-sustained and pressure-driven turbulence in toroidal plasmas is derived. The growth rate of the dressed-test mode, which belongs to the subcritical turbulence, is obtained as a function of the turbulent transport coefficient. In the limit of the low fluctuation level, the mode has the feature of the nonlinear instability and shows the explosive growth. The growth rate vanishes when the driven transport reaches to the stationarily-turbulent level. The stationary solution is thermodynamically stable. The characteristic time, by which the stationary and self-sustained turbulence is established, scales with the ion-sound transit time and is accelerated by the bad magnetic curvature. Influences of the pressure gradient as well as the radial electric field
inhomogeneity are quantified.

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