Logarithm of the squared Lamb and Brunt–Väisälä frequencies (violet and red lines) in terms of the outer mass fraction coordinate. The black points indicate the nodes of the radial eigenfunctions. The upper panel corresponds to a model with log g = 5.12, log T_eff/K = 4.53, M_⋆ = 0.4868 M_⋆ (model HG) with excited modes. The lower panel corresponds to a model with log g = 4.25, log T_eff/K = 4.35, M_⋆ = 0.4908 M_⊙ (model LG) and no excited modes. The region of periods in the range ~880–1130 s is shown with a green strip. This corresponds to the region of excited modes for model HG. At about log(1 − m_r/M_⋆) = −0.2 the Brunt–Väisälä frequency drops to zero in the convective zone. The pulsation driving region is located at the base of this convective zone.