Time evolution of the mean turbulent kinetic energy density E_K (blue) and of the mean magnetic energy density E_M (red) in the convection zone for the four magneto-hydrodynamical (MHD) simulations. Dashed lines represent exponential fits obtained with the kinematic growth rates γ_K listed in Table 2. The top panel is a zoom-in on the first 20 000 s of the turbulent kinetic energy evolution.