ACCURATE HYDROGEN SPECTRAL SIMULATIONS WITH A COMPACT MODEL ATOM

Many large-scale numerical simulations of astrophysical plasmas must a lso reproduce the hydrogen ionization and the resulting emission spect rum, in some cases quite accurately. We describe a compact model hydro gen atom that can be readily incorporated into such simulations. It re produces the recombination efficiency and line spectrum predicted by m uch larger calculations for a very broad range of densities and temper atures. Uncertainties in hydrogen collision data are the largest sourc e of differences between our compact atom and predictions of more exte nsive calculations and underscore the need for accurate atomic data.