An efficient numerical method for time-dependent NLTE radiation transfer

Abstract

We present a numerical method for performing coupled time-dependent radiation transfer and atomic rate equation calculations. The method incorporates the desirable features of time-dependent, non-local thermodynamic equilibrium (NLTE) radiation transfer calculations. It has the advantage that it allows existing time-dependent calculations to be adapted to model time dependent effects. The approximations which are used are discussed.Calculations have been performed for a highly ionised silicon plasma with a single optically thick line. The line is taken to have a top-hat profile which is independent of position. Although the model is simple, it serves to illustrate some important features of time-dependent calculations.