= 0.3$, $\mu = 0$, $\eta_i = 4.0$, $k_{\parallel}^2 = 0.1$ (asterisk) and $k_{\parallel}^2 = 0.0$ (squares). The corresponding quality for the ITG mode is also shown $k_{\parallel}^2 = 0.1$ (plus).](Fig_1_new.eps){height=".3\textheight"}

Second, the slab and toroidally generated zonal flow qualities as a function of $\eta_i$ are compared with the parallel wave number ($k_{\parallel}^2$) as a parameter in Figure 2. The parameters are $\tau = 1$, $k_x = k_y = q_x = 0.3$, $\mu = 0$; $\epsilon_n = 1.0$ and $k_{\parallel}^2 = 0.0$ (asterisk), $k_{\parallel}^2 = 0.1$ (square); $\epsilon_n = 0.0$ and $k_{\parallel}^2 = 0.1$ (diamond). The figure shows that the quality of zonal flows is qualitatively rather insensitive to $\eta_i$, in contrast to the results reported in Ref. [@a26]. The model in Ref. [@a26] is derived using the Wave Kinetic Equation (WKE) and the results are approximately valid in the long wave length limit ($k_{\perp}^2 << 1$ and $k_{\parallel}^2 << 1$). In many aspects the results found comparing the WKE modeling and the coherent mode coupling are qualitatively similar [@a20], [@a23]- [@a26]. In the WKE modeling a strongly decreasing zonal flow quality with increasing $\eta_i$ was found, however in the present model the decrease of zonal flow quality is visible 