Power spectra of the vertical velocity at z = 1.4 Mm from numerical simulations with the photospheric radiative losses estimated from Spiegel (1957). Red lines correspond to cases with the magnetic field set to zero, and blue lines to a magnetic field strength of 2500 G. Solid lines represent the cases with the base of the corona located at z = 2.0 Mm, and dashed lines to cases without a corona or transition region. All the power spectra are normalized to the same value used for the normalization of the power spectra illustrated in Fig. 6.