for larger $\eta_i$ (not shown in the picture). It is also important to note that the difference in quality for slab like and toroidally generated zonal flows are approximately a factor of three. The results are shown for values well above the linear threshold ($\eta_{ith \: slab} = 2/3$ and $\eta_{ith \: tor} \approx 1.8$).

![The zonal flow quality ($\Omega^{IM}/\Omega^{RE}$) as a function of $\eta_i$ for slab like and toroidally generated zonal flows is shown. 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).](Fig_2a.eps){height=".3\textheight"}

In Figure 3 the zonal flow growth rate (positive) and real frequency (negative) (normalized to the ITG mode growth) as a function of $\eta_i$ with $\epsilon_n = 0.0$ (diamond) and $\epsilon_n = 1.0$ (square) are displayed. The other parameters are $\tau = 1$, $k_x = k_y = q_x = 0.3$, $\mu = 0$ and $k_{\parallel}^2 = 0.1$. The figure shows that the zonal flow is exhibiting the same behavior as the linear growth rate in scaling with $\eta_i$. For all values of $\eta_i$ the toroidally generated zonal flows have 