the instability parameter, $\eta$, for modes with the harmonic spherical degrees $\ell = 0,1,2$, as a function of frequency for Models 1 and 2 (the top and bottom panels respectively). Instability parameter measures the net energy gained by a mode during one pulsational cycle and is defined as (Stellingwerf 1978):

$$\label{eta}
  \eta=\frac{W}{\int\limits_0^R\left|\frac{\mathrm{d}W}{\mathrm{d}r}\right|\mathrm{d}r},$$

where $W$ is the global work integral. This definition gives normalization $\eta \in [-1,+1]$. If $\eta > 0$ a pulsation mode is unstable and if $\eta \le 0$ it is stable. There are two global maxima of $\eta$ in Model1, which is similar to the behaviour during the MS evolution (D2013). The first one, at low frequencies, is related to the very high-order g-modes, while the second one, at higher frequencies, is related to the low-order p- and g-modes. All non-radial modes in the second group are mixed modes and they behave like p-modes only in the outer envelope of the star. In the frequency range presented in Fig.\[fig4\], i.e., from 0.04 to 3.5 d$^{-1}$, the values of the radial order, $n$, are in ranges of about $(20,~1700)$ for the $\ell=1$ modes and $n \in (30, 1650)$ for the $\ell=2$ modes. In Model1 the fundamental radial mode and 