PORTA: A three-dimensional multilevel radiative transfer code for modeling the intensity and polarization of spectral lines with massively parallel computers

0421327 - ASÚ 2014 RIV FR eng J - Článek v odborném periodiku
Štěpán, Jiří - Trujillo Bueno, J.
PORTA: A three-dimensional multilevel radiative transfer code for modeling the intensity and polarization of spectral lines with massively parallel computers.
Astronomy & Astrophysics. Roč. 557, September (2013), A143/1-A143/15. ISSN 0004-6361. E-ISSN 1432-0746
Grant CEP: GA ČR GPP209/12/P741
Grant ostatní: EU(XE) COST action MP1104
Institucionální podpora: RVO:67985815
Klíčová slova: line formation * magnetic fields * numerical methods
Kód oboru RIV: BN - Astronomie a nebeská mechanika, astrofyzika
Impakt faktor: 4.479, rok: 2013

Here we present PORTA, an efficient multilevel radiative transfer code we have developed for the simulation of the spectral line polarization caused by scattering processes and the Hanle and Zeeman effects in 3D models of stellar atmospheres. The numerical method of solution is based on the non-linear multigrid iterative method and on a novel short-characteristics formal solver of the Stokes-vector transfer equation which uses monotonic Bezier interpolation. Therefore, with PORTA the computing time needed to obtain at each spatial grid point the self-consistent values of the atomic density matrix (which quantifies the excitation state of the atomic system) scales linearly with the total number of grid points. Another crucial feature of PORTA is its parallelization strategy, which allows us to speed up the numerical solution of complicated 3D problems by several orders of magnitude with respect to sequential radiative transfer approaches, given its excellent linear scaling with the number of available processors. The PORTA code can also be conveniently applied to solve the simpler 3D radiative transfer problem of unpolarized radiation in multilevel systems.
Trvalý link: http://hdl.handle.net/11104/0227672