Application of FBILI method for multi-level line transfer

Abstract

The Forth-and-Back Implicit Lambda Iteration (FBILI) is efficient Gauss-Seidel-type iterative scheme developed by Atanackovic-Vukmanovic et al. [1] for a solution of non-LTE radiative transfer (RT) problems of spectral line formation in stellar atmospheres. In [2] it was more explicitly implemented on non-linear line transfer in multi-level atomic models in 1D geometry, providing high convergence rate to the exact solution with no use of additional acceleration techniques. Here, we apply FBILI on a standard benchmark problem of CaII line formation in the solar atmosphere using the VALCH atmospheric model. Additionally we compare its accuracy with the well known code MULTI.