PORTA: A Massively Parallel Code for 3D Non-LTE Polarized Radiative Transfer

0440052 - ASÚ 2015 RIV US eng C - Konferenční příspěvek (zahraniční konf.)
Štěpán, Jiří
PORTA: A Massively Parallel Code for 3D Non-LTE Polarized Radiative Transfer.
Solar Polarization 7. San Francisco: Astronomical Society of the Pacific, 2014 - (Nagendra, K.), s. 243-244. ASP Conference Series, 489. ISBN 9781583818633.
[Solar Polarization 7. Kunning (CN), 09.09.2013-13.09.2013]
Grant CEP: GA ČR GPP209/12/P741
Institucionální podpora: RVO:67985815
Klíčová slova: non-LTE radiative transfer * PORTA A
Kód oboru RIV: BN - Astronomie a nebeská mechanika, astrofyzika

Here we present PORTA, a computer program we have developed for solving, in three-dimensional (3D) models of stellar atmospheres, the problem of the generation and transfer of spectral line polarization taking into account anisotropic radiation pumping and the Hanle and Zeeman effects in multilevel atoms. The numerical method of solution is based on a highly convergent iterative algorithm, whose convergence rate is insensitive to the grid size, and on an accurate short-characteristics formal solver of the Stokes-vector transfer equation which uses monotonic Bezier interpolation. In addition to the iterative method and the 3D formal solver, another important feature of PORTA is a novel parallelization strategy suitable for taking advantage of massively parallel computers. Linear scaling of the solution with the number of processors allows to reduce the solution time by several orders of magnitude. We present useful benchmarks and a few illustrations of applications using a 3D model of the solar chromosphere resulting from MHD simulations.
Trvalý link: http://hdl.handle.net/11104/0243194