Bibcode
Auer, L.; Bendicho, P. Fabiani; Trujillo Bueno, J.
Referencia bibliográfica
Astronomy and Astrophysics (ISSN 0004-6361), vol. 292, no. 2, p. 599-615
Fecha de publicación:
12
1994
Número de citas
86
Número de citas referidas
70
Descripción
We combine a number of powerful mathematical techniques to produce an
effective method for treating multidimensional radiative transfer
problems in complex atomic models without assuming local thermodynamic
equilibrium (LTE). The approach is so efficient that multilevel
two-dimensional (2D) modeling can now be performed with no more than a
workstation. We employ Accelerated Lambda Iteration (ALI) methods:
accurate short characteristics for the formal solution of the transfer
equation with an efficient new strategy for horizontal periodic boundary
conditions, local approximate Lambda-operators given by the diagonal of
the exact operator, methods to accelerate the convergence, and
preconditioning of the rate equations. Of particular interest is a
simple grid-doubling strategy which both rapidly finds the converged
solution in very fine meshes and also estimates the true error of that
solution. The properties of the method are described in detail with the
help of 2D line-transfer calculations with multilevel model atoms for Ca
II and H. These illustrative multilevel calculations in schematic
inhomogeneous atmospheres demonstrate the importance of properly
including the effects of horizontal radiative transfer and realistic
atomic models.