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Acoustic waves are one of the primary suspects besides magnetic fields forthe chromospheric heating process to temperatures above radiative equilibrium(RE). We derived the mechanical wave energy as seen in line-core velocities toobtain a measure of mechanical energy flux with height for a comparison withthe energy requirements in a semi-empirical atmosphere model. We analyzed a1-hour time series and a large-area map of Ca II H spectra on the traces ofpropagating waves. We analyzed the velocity statistics of several spectrallines in the wing of Ca II H, and the line-core velocity of Ca II H. Weconverted the velocity amplitudes into volume and mass energy densities. Forcomparison, we used the increase of internal energy necessary to lift a REatmosphere to the HSRA temperature stratification. We find that the velocityamplitude grows in agreement with linear wave theory and thus slower withheight than predicted from energy conservation. The mechanical energy of thewaves above around z~500 km is insufficient to maintain the chromospherictemperature rise in the semi-empirical HSRA model. The intensity variations ofthe Ca line core (z~1000 km) can be traced back to the velocity variations ofthe lowermost forming spectral line considered (z~ 250 km). The chromosphericintensity, and hence, (radiation) temperature variations are seen to be inducedby passing waves originating in the photosphere.

The energy of waves in the photosphere and lower chromosphere: 1. Velocity statistics