  Even in quiet areas underneath coronal holes the solar chromosphere contains
ubiquitous heating events. They tend to be small scale and short lived, hence
difficult to identify. Here we do not address their much-debated contribution
to outer-atmosphere heating, but their aftermaths. We performed a statistical
analysis of high-resolution observations in the Balmer H-alpha line to suggest
that many slender dark H-alpha fibrils spreading out from network represent
cooling gas that outlines tracks of preceding rapid type II spicule events or
smaller similar but as yet unresolved heating agents in which the main gas
constituent, hydrogen, ionizes at least partially. Subsequent recombination
then causes dark H-alpha fibrils enhanced by nonequilibrium overopacity. We
suggest that the extraordinary fibrilar appearance of the H-alpha chromosphere
around network results from intermittent, frequent small-scale prior heating.
