(positive) and real frequency (negative) (normalized to $c_s/L_n$) as a function of $k_{\parallel}$ 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 $\eta_i = 4.0$.](Fig_3b.eps){height=".3\textheight"}

Summary
=======

In this paper, a fifth order algebraic dispersion relation for zonal flow generation is derived including the effects of parallel ion motion. The emphasis is on investigating the difference in of zonal flows generated from slab like and toroidal Ion-Temperature-Gradient (ITG) mode turbulence. This is of special interest since it has been found recently that the suppression of turbulence by quasi stationary zonal flows are weak in linear experiments while it is expected that they significantly contribute to turbulence suppression in toroidal devices.

The physical model for the ITG mode are the equations for continuity, temperature and parallel ion motion. The electrons are considered to be Boltzmann distributed and the system of equations is closed by the quasi neutrality condition. The secondary generated zonal flow time evolution is governed by a Hasegawa-Mima like equation. The zonal flow excitation is studied through coupling of coherent modes. The drift wave is considered to be 