Curves showing the maximum absolute value of the cross correlation of the quantities M₃₁ τ′ and M₃₂u′ (Eq. (67)) associated with an overstable mode with λ = 200 m for different values of q, and the values of β used for the plots in Fig. 11. The arrow indicates the direction of increasing β. The monotonic decrease of these curves with increasing q is the reason why the growth rates of overstable modes (Fig. 11) become smaller with increasing q. All curves have been normalized to yield unity for q = 0.