Mean vertical component of the Poynting flux vector S_z (blue) and of the terms (green) and (orange) as a function of height z. The spatial mean is obtained by averaging over the horizontal cross sections of the full computational domain of 9.6 × 9.6 Mm², while the temporal mean is computed from 21 different time instants spread over the time period of the high-cadence series of 15 min. The shaded areas correspond to the standard deviation obtained from the temporal variation.