flows [@a23]- [@a26]. The ITG mode has by now been investigated in many different contexts and situations [@a28]- [@a442]. Anisotropic effects in perpendicular and parallel ion temperature gradient are out of the scope of the present analysis for the zonal flow generation as well as for the linear state [@a441]. The main features of the ITG mode is captured by the more simple model with isotropic ion temperature and temperature gradient [@a443]. Other features often found in the CLM experiment, e.g impurities, do not change the ITG mode qualitatively, however they may contribute though an impurity driven mode [@a444] that in turn may drive a zonal flow. It has also been show that the direct interaction of $\vec{E} \times \vec{B}$ flows with zonal flows are rather weak [@a21], [@a26].

In this particular paper both the slab like and toroidal branch of the ITG mode will be considered as the generating mechanism for the zonal flow. Here, the ITG mode physics is based on the equations for ion continuity, ion temperature and parallel ion motion [@a29]- [@a44]. The system is closed by considering Boltzmann distributed electrons and using the quasi neutrality condition.

The secondary generated zonal flow time evolution is governed 