Time evolution of the runs in Table 2. Upper panel: mean squared values of velocity and generated magnetic field components B_x, B_z of run B128c (Pr = Pr_M = 1) scaled by and respectively. Note the clear exponential growth until t ≈ 1.4t_A0. Fast oscillations in ⟨ U² ⟩ until t ≈ t_A0 indicate g-modes originating from the initial velocity perturbation. Middle panel: mean squared values of generated magnetic field components for different runs. For legend see lower panel. Lower panel: rms value of B_y. Prandtl numbers indicated as (Pr, Pr_M).