The successful modeling of the dynamics of H 2v bright points in the nonmagnetic chromosphere by Carlsson & Stein gave as a by-product a part-time chromosphere lacking the persistent outward temperature increase of time-average empirical models, which is needed to explain observations of UV emission lines and continua. We discuss the failure of the dynamical model to account for most of the observed chromospheric emission, arguing that their model uses only about 1% of the acoustic energy

more »

... ed to the medium. Chromospheric heating requires an additional source of energy in the form of acoustic waves of short period ( minutes), which P ! 2 form shocks and produce the persistent outward temperature increase that can account for the UV emission lines and continua.