Three-dimensional Radiative Transfer with Multilevel Atoms

TL;DR

This paper introduces an efficient 3D radiative transfer formal solver for non-LTE multilevel problems, compatible with polarized and unpolarized media, enabling detailed physical modeling of horizontal radiative effects.

Contribution

It presents a new formal solution method for 3D radiative transfer with periodic boundary conditions, integrated into a multilevel non-LTE code for improved physical accuracy.

Findings

Demonstrated the solver's ability to model horizontal radiative transfer effects.

Validated the method with schematic 3D multilevel calculations.

Enhanced the accuracy of non-LTE radiative transfer modeling.

Abstract

The efficient numerical solution of Non-LTE multilevel transfer problems requires the combination of highly convergent iterative schemes with fast and accurate formal solution methods of the radiative transfer (RT) equation. This contribution begins presenting a method for the formal solution of the RT equation in three-dimensional (3D) media with horizontal periodic boundary conditions. This formal solver is suitable for both, unpolarized and polarized 3D radiative transfer and it can be easily combined with the iterative schemes for solving non-LTE multilevel transfer problems that we have developed over the last few years. We demonstrate this by showing some schematic 3D multilevel calculations that illustrate the physical effects of horizontal radiative transfer. These Non-LTE calculations have been carried out with our code MUGA 3D, a 3D multilevel Non-LTE code based on the Gauss-Seidel iterative scheme that Trujillo Bueno and Fabiani Bendicho (1995) developed for RT applications.