J/A+A/573/A72Planetary atmosphere radiative transport code (Garcia Munoz+ 2015)

Pre-conditioned backward Monte Carlo solutions to radiative transport in planetary atmospheres. Fundamentals: Sampling of propagation directions in polarising media. Garcia Munoz A., Mills F.P. <Astron. Astrophys. 573, A72 (2015)> =2015A&A...573A..72GADC_Keywords: Models, atmosphere ; PlanetsKeywords: polarization - radiative transportAbstract: The interpretation of polarised radiation emerging from a planetary atmosphere must rely on solutions to the vector Radiative Transport Equation (vRTE).Monte Carlo integration of the vRTE is a valuable approach for its flexible treatment of complex viewing and/or illumination geometries and because it can intuitively incorporate elaborate physics. We present a novel Pre-Conditioned Backward Monte Carlo (PBMC) algorithm for solving the vRTE and apply it to planetary atmospheres irradiated from above. As classical BMC methods, our PBMC algorithm builds the solution by simulating the photon trajectories from the detector towards the radiation source, i.e. in the reverse order of the actual photon displacements. We show that the neglect of polarisation in the sampling of photon propagation directions in classical BMC algorithms leads to unstable and biased solutions for conservative, optically-thick, strongly-polarising media such as Rayleigh atmospheres. The numerical difficulty is avoided by pre-conditioning the scattering matrix with information from the scattering matrices of prior (in the BMC integration order) photon collisions. Pre-conditioning introduces a sense of history in the photon polarisation states through the simulated trajectories.Description: Files are: * readme.txt * Input files: INPUT_hazeL.txt, INPUT_L13.txt, INPUT_L60.txt; they contain explanations to the input parameters. Copy INPUT_XXXX.txt into INPUT.dat to execute some of the examples described in the reference. * Files with scattering matrix properties: phF_hazeL.txt, phF_L13.txt, phF_L60.txt * Script for compilation in GFortran (myscript)File Summary:

FileName Lrecl Records Explanations

ReadMe 80 . This file readme.txt 79 62 Explanations INPUT.dat 100 37 Input file INPUT_L13.txt 100 46 Input file INPUT_L60.txt 100 46 Input file INPUT_hazeL.txt 100 47 Input file PBMC.f90 164 1019 Fortran code myscript 51 1 Script for compilation in GFortran phF_L13.txt 63 1801 File with scattering matrix properties phF_L60.txt 63 1801 File with scattering matrix properties phF_hazeL.txt 63 1801 File with scattering matrix properties

Acknowledgements: Antonio Garcia Munoz, tonhingm(at)gmail.com(End)Patricia Vannier [CDS] 26-Aug-2014

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