Evidence for short-period acoustic waves in the solar atmosphere

Short-period acoustic waves are thought to supply the energy for the radiative losses of the non-magnetic chromosphere of the Sun and, in general, of late-type stars. Here, we present evidence for the existence of waves in the solar atmosphere with periods in the range of 50s < P < 100 s. Two-dimensional time sequences with a cadence of 25 s were obtained from quiet Sun disk center in Fe I 5434 Angstrom. The observations were performed with the Gottingen Fabry-Perot spectrometer in the Vacuum Tower Telescope at the Observatorio del Teide/Tenerife. They are subjected to speckle reconstruction and to a wavelet analysis. The atmospheric ranges forming the velocity signals are narrowed by linear combinations of Doppler maps from wavelengths near line center. The power in the short-period range is concentrated above intergranular spaces. We estimate an acoustic flux into the chromosphere of approximately 3 x 10(6) erg cm(-2) s(-1), as needed for the chromospheric radiative losses.