= 0$, $\eta_i = 4.0$, $k_{\parallel}^2 = 0.1$ (asterisk) and $k_{\parallel}^2 = 0.0$ (squares). Shown in Figure 1 is also the corresponding quality for the ITG mode $k_{\parallel}^2 = 0.1$ (plus). The parameters used in this paper are chosen as realistic values of a tokamak and for easy comparison of the results. The Figure shows a rapidly increasing quality of zonal flows with increasing $\epsilon_n = 2L_n/R$. A large negative value of the quality is more beneficial. The qualitative behavior of the model in a variation of the parallel wave number is similar except that for small or vanishing $\epsilon_n$ the slab-like mode generated zonal flows are captured. This is clearly indicating a stronger suppression effect of toroidally generated zonal flows. This result is to be compared with the absolute values of zonal flow growth rate and real frequency shown in Figure 2 in Ref. [@a20]. The quality of the ITG mode shows a significantly different qualitative behavior (opposite trend) than the corresponding values for the zonal flow.

![The zonal flow quality ($\Omega^{IM}/\Omega^{RE}$) as a function of $\epsilon_n$ with the parallel wave number ($k_{\parallel}^2$) as a parameter is displayed. The parameters are $\tau = 1$, $k_x = k_y = q_x 