Effect of triangularity on ion-temperature-gradient-driven turbulence

The linear and nonlinear properties of ion-temperature-gradient-driven turbulence with adiabatic electrons are modeled for axisymmetric configurations for a broad range of triangularities delta, both negative and positive. Peak linear growth rates decrease with negative delta but increase and shift toward a finite radial wavenumber k(x) with positive delta. The growth-rate spectrum broadens as a function of k(x) with negative delta and significantly narrows with positive delta. The effect of triangularity on linear instability properties can be explained through its impact on magnetic polarization and curvature. Nonlinear heat flux is weakly dependent on triangularity for | delta | & LE; 0.5, decreasing significantly with extreme delta, regardless of sign. Zonal modes play an important role in nonlinear saturation in the configurations studied, and artificially suppressing zonal modes increased nonlinear heat flux by a factor of about four for negative delta, increasing with positive delta by almost a factor of 20. Proxies for zonal-flow damping and drive suggest that zonal flows are enhanced with increasing positive delta.

Automated summary

The study investigated the effects of triangularity on the linear and nonlinear properties of ion-temperature-gradient-driven turbulence. It was found that triangularity significantly influences the linear growth rates and nonlinear heat flux, with negative delta suppressing zonal modes and positive delta enhancing zonal flows.