Observation of a short-lived pattern in the solar chromosphere

Aims.In this work we investigate the dynamic behavior of inter-network regions of the solar chromosphere. Methods.We observed the chromosphere of the quiet Sun using a narrow-band Lyot filter centered at the $\ion{Ca}{ii}$ K2v emission peak with a bandpass of 0.3 Å. We achieved a spatial resolution of on average 0$\farcs$ 7 at a cadence of 10 s. Results.In the inter-network we find a mesh-like pattern that features bright grains at the vertices. The pattern has a typical spatial scale of 1$\farcs$ 95 and a mean evolution time scale of 53 s with a standard deviation of 10 s. A comparison of our results with a recent three-dimensional radiation hydrodynamical model implies that the observed pattern is of chromospheric origin. The measured time scales are not compatible with those of reversed granulation in the photosphere although the appearance is similar. A direct comparison between network and inter-network structure shows that their typical time scales differ by at least a factor of two. Conclusions.The existence of a rapidly evolving small-scale pattern in the inter-network regions supports the picture of the lower chromosphere as a highly dynamical and intermittent phenomenon