On the validity of acoustically heated chromosphere models

Theoretical models of solar and stellar chromospheres heated by acoustic waves have so far been constructed by using time-dependent, one-dimensional, radiation-hydrodynamic numerical codes that are based on the approximation of plane-parallel geometry. The approach seems to be justified by the fact that the chromospheres of most stars extend over very narrow height ranges compared to the stellar radius. It is demonstrated that this commonly used assumption may lead to unrealistic shock mergings, to the artificial formation of unusually strong shocks and the artificial destruction of high-frequency acoustic wave power. Comparing one-dimensional calculations with observations may lead to severe misjudgment about the nature of chromospheric heating.