Difference of δ = ∇_ađ – ∇ between the adiabatic thermal gradient and the actual stellar thermal gradient (upper panel) and the Brunt-Väisäla frequency N (lower panel) vs. the stellar radius r in units of the photospheric radius R (red solid lines). The vertical green dashed lines bound a layer of thickness L_p = 0.1 H_p, where H_p is the pressure scale height at the base of the stellar convection zone.