2-DIMENSIONAL RADIATIVE-TRANSFER WITH PARTIAL FREQUENCY REDISTRIBUTION .1. GENERAL-METHOD

We present a new method for the solution of non-LTE scattering problems in two dimensions. It is based on Accelerated Lambda Iteration and an improved short characteristic method. It is more than an order of magnitude faster than a direct approach for Complete Redistribution. We, further, have extended the method to the solution of Partial Redistribution problems. The computational cost of treating PRD with the new method is only a small factor larger than CRD. Results with the new iterative approach are in complete agreement with previously published results.