A distribution function calculation of the Hα profiles of high-velocity shocks - II. The broad component neutral precursor
A self-consistent kinetic/fluid model is used to calculate the effect of different pre-shock ionization fractions upon the Hα line profiles from a non-radiative shock. The model relaxes the neutral velocity distribution from initial conditions through the ionic shock, and calculates the energy and momentum deposition into the pre-shock region by the broad component neutral precursor. The observed widths of the narrow component of twin-component Hα line profiles are in the 30-50 km s^-1 range, implying the presence of a precursor. We find that although in our models the temperature of the ions in the neutral precursor is in the range implied by these widths, the precursor size is too small to result in the observed broadening for the parameters studied. The line widths of the narrow component are only weakly dependent upon neutral fraction, and a large variation is seen in the broad component width owing to damping of the ion shock. It is also found that the broad component of the model line profiles has a significant deviation from a Gaussian shape in the face-on case.