PAKAL: A THREE-DIMENSIONAL MODEL TO SOLVE THE RADIATIVE TRANSFER EQUATION

Journal Article · Tue Jun 15 00:00:00 EDT 2010 · Astrophysical Journal, Supplement Series

DOI:https://doi.org/10.1088/0067-0049/188/2/437· OSTI ID:21455248

De la Luz, Victor; Lara, Alejandro ^[1]; Mendoza-Torres, J E ^[2]; Selhorst, Caius L ^[3]

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1. Instituto de Geofisica, Universidad Nacional Autonoma de Mexico, 04510 (Mexico)
2. Coordinacion de Astrofisica, Instituto Nacional de Astrofisica Optica y Electronica, 72840 (Mexico)
3. CRAAM, Universidade Presbiteriana Mackenzie, Sao Paulo, SP 01302-907 (Brazil)

We present a new numerical model called 'Pakal' intended to solve the radiative transfer equation in a three-dimensional (3D) geometry, using the approximation for a locally plane-parallel atmosphere. Pakal uses pre-calculated radial profiles of density and temperature (based on hydrostatic, hydrodynamic, or MHD models) to compute the emission from 3D source structures with high spatial resolution. Then, Pakal solves the radiative transfer equation in a set of (3D) ray paths, going from the source to the observer. Pakal uses a new algorithm to compute the radiative transfer equation by using an intelligent system consisting of three structures: a cellular automaton; an expert system; and a program coordinator. The code outputs can be either two-dimensional maps or one-dimensional profiles, which reproduce the observations with high accuracy, giving detailed physical information about the environment where the radiation was generated and/or transmitted. We present the model applied to a 3D solar radial geometry, assuming a locally plane-parallel atmosphere, and thermal free-free radio emission from hydrogen-helium gas in thermodynamic equilibrium. We also present the convergence test of the code. We computed the synthetic spectrum of the centimetric-millimetric solar emission and found better agreement with observations (up to 10{sup 4} K at 20 GHz) than previous models reported in the literature. The stability and convergence test show the high accuracy of the code. Finally, Pakal can improve the integration time by up to an order of magnitude compared against linear integration codes.

• OSTI ID: 21455248
• Journal Information: Astrophysical Journal, Supplement Series, Vol. 188, Issue 2; Other Information: DOI: 10.1088/0067-0049/188/2/437; ISSN 0067-0049
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
CHROMOSPHERE
HELIUM
HYDROGEN
MAGNETOHYDRODYNAMICS
SOLAR RADIATION
SUN
THREE-DIMENSIONAL CALCULATIONS
ATMOSPHERES
ELEMENTS
FLUID MECHANICS
FLUIDS
GASES
HYDRODYNAMICS
MAIN SEQUENCE STARS
MECHANICS
NONMETALS
RADIATIONS
RARE GASES
SOLAR ATMOSPHERE
STARS
STELLAR ATMOSPHERES
STELLAR RADIATION