is visible for larger $\eta_i$ (not shown explicitly in this paper). In all parameter scalings the coherent mode coupling model agrees well with a model derived using the WKE model for the same background physics.

It is also shown that the slab like generated zonal flows are driven by the acoustic waves through the ITG mode. This is the reason for the comparatively larger real frequency of the slab like driven zonal flow. The growth rate and real frequency for the toroidally generated zonal flows are only weakly dependent on the parallel wave number.

To this end, in terms of quality, the toroidally driven zonal flows have higher values compared to the slab like generated zonal flows such as those found in CLM. The slab like generated zonal flows are inherently more oscillating zonal flows and hence the turbulence suppression found is much smaller. [@a19] It should also be noted that the toroidally generated zonal flows exhibit large values of the growth rate ($\Omega^{IM}/\gamma_{ITG}>1$) compared to the slab case. All these results support the findings that the turbulence suppression is smaller in linear devices with small curvature (in the present paper represented with small $\epsilon_n$). There are still some unknown 