High resolution spectroscopy of the disk chromosphere

We describe time-series observations of small-scale Ca ii emission features located outside the network in the quiet chromosphere. Simultaneous spectra in K and λ 8542 show unambiguously that the evolutionary behaviour of the K-line profile due to an outwardly propagating velocity pulse. Assuming that this pulse is a progressive acoustic wave, as suggested by the inferred flow parameters, we show that the wave loses mechanical energy in traversing the chromosphere. This implies that the bright Ca ii features (K-grains) are the manifestation of local heating in the chromosphere, possibly by shock waves.