Profiles of dimensions and acceleration of convective elements across the most external convective region of a low mass star. Left panel: dimension reached by the convective elements at t_asy as a function of log P. Since t_asy decreases, the velocity and dimensions of the convective elements in these very external layers are also expected to decrease going toward the adiabatic fall layer. Right panel: radial acceleration of a convective element as a function of the depth (log P) across the external convective zone of the stellar models representing the Sun (thin solid lines with triangles). With respect to the layer of the adiabatic fall (at log P = 5.4 dyn cm⁻²), the left branch of the curve (red triangles) is for ξ_e > D, i.e., Eq. (51), whereas the right branch (blue triangles) is for ξ_e < D, i.e., Eq. (52), and the minimum of the acceleration “coincides” with the value of ≃300 cm s⁻² given by the SFCT, see Eq. (50). The horizontal dotted line is the nearly constant acceleration from the MLT.