Dependence of the cycle amplitude on the convection zone diffusivity (η_c) at different peak meridional flow speeds (V_θp). For high peak meridional flow speed (V_θp = 15, 20 m s⁻¹), the cycle amplitude first increases and then decreases with increasing η_c, whereas for low peak meridional flow speed (V_θp = 10, 12.5 m s⁻¹), the cycle amplitude continuously decreases with increasing η_c.