RAPIDLY CONVERGENT LAMBDA-OPERATOR METHOD FOR SOLVING RESONANCE LINE SCATTERING IN PLANETARY-ATMOSPHERES .1. THE ONE-DIMENSIONAL SLAB

The study of planetary atmospheric atomic and molecular (resonance) li ne emissions often require sophisticated radiative transfer models to properly account for scattering and absorption effects, In this work a relatively new and simple, yet powerful, numerical technique for solv ing radiative transfer problems has been developed and coded for a two -level atom in an one-dimensional Cartesian coordinate system. Angular scattering is assumed to be isotropic, and the method has been tested for monochromatic, complete frequency redistribution, and angle-avera ged frequency redistribution. Formally, the solution is based on the c ommonly known lambda operator method. Rapid and robust convergence is attained using an intermediate operator that is readily evaluated. In addition, bilinear extrapolation based on previous iterates is found t o further increase the rate of convergence. The one-dimensional model intensity versus frequency profiles are found to compare favorably wit h those of other proven models over a large-range of optical depths.