ACOUSTIC HEATING OF THE CHROMOSPHERE AND COOL CORONA IN THE F-STAR ALPHA-CANIS-MINORIS (PROCYON)

We report on a hydrodynamical model of acoustic wave energy deposition in the atmosphere of the F star Procyon. The model treats radiative losses in the photosphere by solving the continuum radiative transfer (RT) problem; it treats radiative losses in the chromosphere by solving the RT equation in two representative strong lines (Mg II k and Ly alpha); and it includes optically thin emission from the corona. We find a temperature minimum of 4440 K and a transition region at a height of 3500-4000 km above the photosphere. Our acoustic model accounts for the reported fluxes of Mg II and Ly alpha emission lines, as well as for the X-ray flux from the cool (T < 1 MK) coronal component reported by Lemen et al. (1989). The differential emission measure distribution in our model agrees quite well with empirical results of Jordan et al. (1986).