Time‐dependent Monte Carlo Radiative Transfer Calculations for Three‐dimensional Supernova Spectra, Light Curves, and Polarization

Abstract. The MYSTIC three-dimensional Monte-Carlo radiative transfer model has been extended to simulate solar and thermal irradiances with a rigorous consideration of topography. Forward as well as backward Monte Carlo simulations are possible for arbitrarily oriented surfaces and we demonstrate that the backward Monte Carlo technique is superior to the forward method for applications involving topography, by greatly reducing the computational demands. MYSTIC is used to simulate the short- and longwave radiation fields during a clear day and night in and around Arizona's Meteor Crater, a bowl-shaped, 165-m-deep basin with a diameter of 1200 m. The simulations are made over a 4 by 4 km domain using a 10-m horizontal resolution digital elevation model and meteorological input data collected during the METCRAX (Meteor Crater Experiment) field experiment in 2006. Irradiance (or radiative flux) measurements at multiple locations inside the crater are then used to evaluate the simulations. MYSTIC is shown to realistically model the complex interactions between topography and the radiative field, resolving the effects of terrain shading, terrain exposure, and longwave surface emissions. The effects of surface temperature variations and of temperature stratification within the crater atmosphere on the near-surface longwave irradiance are then evaluated with additional simulations.

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3-D radiative transfer in large-eddy simulations – experiences coupling the TenStream solver to the UCLA–LES

Geoscientific Model Development Discussions ◽

10.5194/gmdd-8-9021-2015 ◽

2015 ◽

Vol 8 (10) ◽

pp. 9021-9043 ◽

Cited By ~ 1

Author(s):

F. Jakub ◽

B. Mayer

Keyword(s):

Monte Carlo ◽

Radiative Transfer ◽

Three Dimensional ◽

Spectral Integration ◽

Large Eddy ◽

Complex Scenes ◽

Cloud Resolving Model ◽

Strong Scaling ◽

Overall Performance ◽

Spectral Sampling

Abstract. The recently developed three-dimensional TenStream radiative transfer solver was integrated into the UCLA–LES cloud resolving model. This work documents the overall performance of the TenStream solver as well as the technical challenges migrating from 1-D schemes to 3-D schemes. In particular the employed Monte-Carlo-Spectral-Integration needed to be re-examined in conjunction with 3-D radiative transfer. Despite the fact that the spectral sampling has to be performed uniformly over the whole domain, we find that the Monte-Carlo-Spectral-Integration remains valid. To understand the performance characteristics of the coupled TenStream solver, we conducted weak- as well as strong-scaling experiments. In this context, we investigate two matrix-preconditioner (GAMG and block-jacobi ILU) and find that algebraic multigrid preconditioning performs well for complex scenes and highly parallelized simulations. The TenStream solver is tested for up to 4096 cores and shows a parallel scaling efficiency of 80–90 % on various supercomputers. Compared to the widely employed 1-D δ-Eddington two-stream solver, the computational costs for the radiative transfer solver alone increases by a factor of five to ten.

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PAH in Vectorized Three Dimensional Monte Carlo Dust Radiative Transfer Models

PAHs and the Universe ◽

10.1051/978-2-7598-2482-3-032 ◽

2020 ◽

pp. 285-290

Author(s):

R. Siebenmorgen ◽

F. Heymann ◽

E. Krugel

Keyword(s):

Monte Carlo ◽

Radiative Transfer ◽

Three Dimensional ◽

Radiative Transfer Models ◽

Transfer Models

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possis: predicting spectra, light curves, and polarization for multidimensional models of supernovae and kilonovae

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2495 ◽

2019 ◽

Vol 489 (4) ◽

pp. 5037-5045 ◽

Cited By ~ 20

Author(s):

M Bulla

Keyword(s):

Radiation Transport ◽

Three Dimensional ◽

Polar Axis ◽

Light Curves ◽

Time Dependent ◽

Opening Angle ◽

Monte Carlo Code ◽

Lanthanide Elements ◽

The Impact ◽

Multidimensional Models

ABSTRACT We present possis, a time-dependent three-dimensional Monte Carlo code for modelling radiation transport in supernovae and kilonovae. The code incorporates wavelength- and time-dependent opacities, and predicts viewing-angle dependent spectra, light curves, and polarization for both idealized and hydrodynamical explosion models. We apply the code to a kilonova model with two distinct ejecta components, one including lanthanide elements with relatively high opacities and the other devoid of lanthanides and characterized by lower opacities. We find that a model with total ejecta mass $M_\mathrm{ej}=0.04\, \mathrm{M}_\odot$ and half-opening angle of the lanthanide-rich component Φ = 30° provides a good match to GW 170817/AT 2017gfo for orientations near the polar axis (i.e. for a system viewed close to face-on). We then show how crucial is the use of self-consistent multidimensional models in place of combining one-dimensional models to infer important parameters, such as the ejecta masses. We finally explore the impact of Mej and Φ on the synthetic observables and highlight how the relatively fast computation times of possis make it well-suited to perform parameter-space studies and extract key properties of supernovae and kilonovae. Spectra calculated with possis in this and future studies will be made publicly available.

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Monte-Carlo methods for NLTE spectral synthesis of supernovae

Astronomy and Astrophysics ◽

10.1051/0004-6361/201833043 ◽

2018 ◽

Vol 620 ◽

pp. A156 ◽

Cited By ~ 7

Author(s):

M. Ergon ◽

C. Fransson ◽

A. Jerkstrand ◽

C. Kozma ◽

M. Kromer ◽

...

Keyword(s):

Monte Carlo ◽

Radiative Transfer ◽

Radiation Field ◽

Spectral Synthesis ◽

Time Dependent ◽

Thermal Excitation ◽

Chain Model ◽

Full Time ◽

Emission Frequency ◽

Radiative Transfer Problem

We present JEKYLL, a new code for modelling of supernova (SN) spectra and lightcurves based on Monte-Carlo (MC) techniques for the radiative transfer. The code assumes spherical symmetry, homologous expansion and steady state for the matter, but is otherwise capable of solving the time-dependent radiative transfer problem in non-local-thermodynamic-equilibrium (NLTE). The method used was introduced in a series of papers by Lucy, but the full time-dependent NLTE capabilities of it have never been tested. Here, we have extended the method to include non-thermal excitation and ionization as well as charge-transfer and two-photon processes. Based on earlier work, the non-thermal rates are calculated by solving the Spencer-Fano equation. Using a method previously developed for the SUMO code, macroscopic mixing of the material is taken into account in a statistical sense. To save computational power a diffusion solver is used in the inner region, where the radiation field may be assumed to be thermalized. In addition, a statistical Markov-chain model is used to sample the emission frequency more efficiently, and we introduce a method to control the sampling of the radiation field, which is used to reduce the noise in the radiation field estimators. Except for a description of JEKYLL, we provide comparisons with the ARTIS, SUMO and CMFGEN codes, which show good agreement in the calculated spectra as well as the state of the gas. In particular, the comparison with CMFGEN, which is similar in terms of physics but uses a different technique, shows that the Lucy method does indeed converge in the time-dependent NLTE case. Finally, as an example of the time-dependent NLTE capabilities of JEKYLL, we present a model of a Type IIb SN, taken from a set of models presented and discussed in detail in an accompanying paper. Based on this model we investigate the effects of NLTE, in particular those arising from non-thermal excitation and ionization, and find strong effects even on the bolometric lightcurve. This highlights the need for full NLTE calculations when simulating the spectra and lightcurves of SNe.

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