Computing Temperatures in Optically Thick Protoplanetary Disks

Capuder, Lawrence F.. Jr.

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NASA NTRS · 20150006576

Computing Temperatures in Optically Thick Protoplanetary Disks

Capuder, Lawrence F.. Jr.

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Abstract

We worked with a Monte Carlo radiative transfer code to simulate the transfer of energy through protoplanetary disks, where planet formation occurs. The code tracks photons from the star into the disk, through scattering, absorption and re-emission, until they escape to infinity. High optical depths in the disk interior dominate the computation time because it takes the photon packet many interactions to get out of the region. High optical depths also receive few photons and therefore do not have well-estimated temperatures. We applied a modified random walk (MRW) approximation for treating high optical depths and to speed up the Monte Carlo calculations. The MRW is implemented by calculating the average number of interactions the photon packet will undergo in diffusing within a single cell of the spatial grid and then updating the packet position, packet frequencies, and local radiation absorption rate appropriately. The MRW approximation was then tested for accuracy and speed compared to the original code. We determined that MRW provides accurate answers to Monte Carlo Radiative transfer simulations. The speed gained from using MRW is shown to be proportional to the disk mass.

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Capuder, Lawrence F.. Jr.. 2011-08-01. Computing Temperatures in Optically Thick Protoplanetary Disks. https://ntrs.nasa.gov/citations/20150006576

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