Dynamics of the solar atmosphere. IV - Evanescent waves of small amplitude

The phase spectra of velocity and brightness perturbations in the quiet photosphere have been studied in the evanescent domain of the k-omega diagram. A regime of low-amplitude evanescent motions, occupying a large sector of the diagnostic diagram bordered by the Lamb and the fundamental mode, has been discovered. This regime forms a continuum in the k-omega plane, in contrast to the 5-min oscillations. Beyond the fundamental mode, it extends to much higher frequencies in between the power ridges of the resonant p-modes. It is suggested that the observed V-I phase is characteristic of evanescent waves, whose progressive part carries energy downward, and that a continuum of such waves is produced through scattering of ordinary resonant p-modes at higher levels in the atmosphere.