scholarly journals Observational constraints on the origin of the elements

2020 ◽  
Vol 634 ◽  
pp. A55 ◽  
Author(s):  
A. J. Gallagher ◽  
M. Bergemann ◽  
R. Collet ◽  
B. Plez ◽  
J. Leenaarts ◽  
...  
Keyword(s):  
Radiative Transfer ◽  
Three Dimensional ◽  
Solar Spectrum ◽  
Random Errors ◽  
Exchange Reactions ◽  
One Dimensional ◽  
Optical Region ◽  
Non Local ◽  
First Time ◽  
Model Atom

Context. The pursuit of more realistic spectroscopic modelling and consistent abundances has led us to begin a new series of papers designed to improve current solar and stellar abundances of various atomic species. To achieve this, we have begun updating the three-dimensional (3D) non-local thermodynamic equilibrium (non-LTE) radiative transfer code, MULTI3D, and the equivalent one-dimensional (1D) non-LTE radiative transfer code, MULTI 2.3. Aims. We examine our improvements to these codes by redetermining the solar barium abundance. Barium was chosen for this test as it is an important diagnostic element of the s-process in the context of galactic chemical evolution. New Ba II + H collisional data for excitation and charge exchange reactions computed from first principles had recently become available and were included in the model atom. The atom also includes the effects of isotopic line shifts and hyperfine splitting. Methods. A grid of 1D LTE barium lines were constructed with MULTI 2.3 and fit to the four Ba II lines available to us in the optical region of the solar spectrum. Abundance corrections were then determined in 1D non-LTE, 3D LTE, and 3D non-LTE. A new 3D non-LTE solar barium abundance was computed from these corrections. Results. We present for the first time the full 3D non-LTE barium abundance of A(Ba) = 2.27 ± 0.02 ± 0.01, which was derived from four individual fully consistent barium lines. Errors here represent the systematic and random errors, respectively.

scholarly journals The on-axis magnetic well and Mercier's criterion for arbitrary stellarator geometries

2021 ◽  
Vol 87 (2) ◽  
Author(s):  
P. Kim ◽  
R. Jorge ◽  
W. Dorland
Keyword(s):  
Magnetic Field ◽  
Original Work ◽  
Three Dimensional ◽  
Radial Distance ◽  
Analytical Form ◽  
One Dimensional ◽  
Modern Notation ◽  
Magnetic Well ◽  
First Time ◽  
Dimensional Integral

A simplified analytical form of the on-axis magnetic well and Mercier's criterion for interchange instabilities for arbitrary three-dimensional magnetic field geometries is derived. For this purpose, a near-axis expansion based on a direct coordinate approach is used by expressing the toroidal magnetic flux in terms of powers of the radial distance to the magnetic axis. For the first time, the magnetic well and Mercier's criterion are then written as a one-dimensional integral with respect to the axis arclength. When compared with the original work of Mercier, the derivation here is presented using modern notation and in a more streamlined manner that highlights essential steps. Finally, these expressions are verified numerically using several quasisymmetric and non-quasisymmetric stellarator configurations including Wendelstein 7-X.

scholarly journals Understanding nebular spectra of Type Ia supernovae

2020 ◽  
Vol 494 (2) ◽  
pp. 2221-2235 ◽  
Author(s):  
Kevin D Wilk ◽  
D John Hillier ◽  
Luc Dessart
Keyword(s):  
Radiative Transfer ◽  
Local Thermodynamic Equilibrium ◽  
Diagnostic Feature ◽  
Type Ia Supernovae ◽  
Thermal Heating ◽  
One Dimensional ◽  
Type Ia ◽  
Natural Mechanism ◽  
Non Local ◽  
Ia Supernovae

ABSTRACT In this study, we present one-dimensional, non-local-thermodynamic-equilibrium, radiative transfer simulations (using cmfgen) in which we introduce micro-clumping at nebular times into two Type Ia supernova ejecta models. We use one sub-Chandrasekhar (sub-MCh) ejecta model with 1.04 M⊙ and one Chandrasekhar (MCh) ejecta model with 1.40 M⊙. We introduce clumping factors f = 0.33, 0.25, and 0.10, which are constant throughout the ejecta, and compare results to the unclumped f = 1.0 case. We find that clumping is a natural mechanism to reduce the ionization of the ejecta, reducing emission from [Fe iii], [Ar iii], and [S iii] by a factor of a few. For decreasing values of the clumping factor f, the [Ca ii] λλ7291,7324 doublet became a dominant cooling line for our MCh model but remained weak in our sub-MCh model. Strong [Ca ii] λλ7291,7324 indicates non-thermal heating in that region and may constrain explosion modelling. Due to the low abundance of stable nickel, our sub-MCh model never showed the [Ni ii] 1.939-μm diagnostic feature for all clumping values.

Three Dimensional Radiative Transfer in ICON-LEM

2020 ◽  
Author(s):  
Fabian Jakub ◽  
Bernhard Mayer
Keyword(s):  
Radiative Transfer ◽  
Detrimental Effect ◽  
Energy Transport ◽  
Three Dimensional ◽  
Cloud Formation ◽  
One Dimensional ◽  
3D Effects ◽  
Computational Simplicity ◽  
Boundary Layer Dynamics ◽  
Side Illumination

<pre class="moz-quote-pre">Recent studies have shown that the effects of three dimensional radiative transfer may impact cloud formation and precipitation. While one-dimensional solvers are favoured due to their computational simplicity, they do however neglect any horizontal energy transport. In particular, the 1D approximation neglects 3D effects such as cloud side illumination and the displacement of the cloud's shadow at the surface which are relevant whenever the sun is not in the zenith. This has a detrimental effect on the results of high resolution simulations. 3D radiative transfer has the potential to considerably change the boundary layer dynamics, the evolution of clouds, their lifetime and precipitation onset. To this date, studies that investigate the influence of 3D effects on realistic NWP settings are rare, primarily because there haven't been 3D radiative transfer solvers around that were fast enough to be run interactively in a forecast simulation. For that purpose we adapted the TenStream solver (parallel 3D radiative transfer solver for LES) to unstructured meshes and coupled it to ICON-LEM. We will present the new solver in the context of ICON-LEM simulations, the methodologies used and its characteristics.</pre>

scholarly journals Three-dimensional effects in polarization signatures as observed from precipitating clouds by low frequency ground-based microwave radiometers

2006 ◽  
Vol 6 (3) ◽  
pp. 5427-5456
Author(s):  
A. Battaglia ◽  
C. Simmer ◽  
H. Czekala
Keyword(s):  
Radiative Transfer ◽  
Monte Carlo Model ◽  
Three Dimensional ◽  
Low Frequency ◽  
Radiative Transfer Model ◽  
Observation Angle ◽  
Transfer Model ◽  
One Dimensional ◽  
Dimensional Effects ◽  
The Impact

Abstract. Consistent negative polarization differences (i.e. differences between the vertical and the horizontal brightness temperature) are observed when looking at precipitating systems by ground-based radiometers at slant angles. These signatures can be partially explained by one-dimensional radiative transfer computations that include oriented non-spherical raindrops. However some cases are characterized by polarization values that exceed differences expected from one-dimensional radiative transfer. A three-dimensional fully polarized Monte Carlo model has been used to evaluate the impact of the horizontal finiteness of rain shafts with different rain rates at 10, 19, and 30 GHz. The results show that because of the reduced slant optical thickness in finite clouds, the polarization signal can strongly differ from its one-dimensional counterpart. At the higher frequencies and when the radiometer is positioned underneath the cloud, significantly higher negative values for the polarization are found which are also consistent with some observations. When the observation point is located outside of the precipitating cloud, typical polarization patterns (with troughs and peaks) as a function of the observation angle are predicted. An approximate 1-D slant path radiative transfer model is considered as well and results are compared with the full 3-D simulations to investigate whether or not three-dimensional effects can be explained by geometry effects alone. The study has strong relevance for low-frequency passive microwave polarimetric studies.

scholarly journals Reduction of radiation biases by incorporating the missing cloud variability by means of downscaling techniques: a study using the 3-D MoCaRT model

2012 ◽  
Vol 5 (9) ◽  
pp. 2261-2276 ◽  
Author(s):  
S. Gimeno García ◽  
T. Trautmann ◽  
V. Venema
Keyword(s):  
Radiative Transfer ◽  
Spatial Resolution ◽  
Heterogeneous Media ◽  
Monte Carlo Model ◽  
Computational Cost ◽  
Three Dimensional ◽  
Accurate Solution ◽  
Stochastic Methods ◽  
Climate Modelling ◽  
One Dimensional

Abstract. Handling complexity to the smallest detail in atmospheric radiative transfer models is unfeasible in practice. On the one hand, the properties of the interacting medium, i.e., the atmosphere and the surface, are only available at a limited spatial resolution. On the other hand, the computational cost of accurate radiation models accounting for three-dimensional heterogeneous media are prohibitive for some applications, especially for climate modelling and operational remote-sensing algorithms. Hence, it is still common practice to use simplified models for atmospheric radiation applications. Three-dimensional radiation models can deal with complex scenarios providing an accurate solution to the radiative transfer. In contrast, one-dimensional models are computationally more efficient, but introduce biases to the radiation results. With the help of stochastic models that consider the multi-fractal nature of clouds, it is possible to scale cloud properties given at a coarse spatial resolution down to a higher resolution. Performing the radiative transfer within the cloud fields at higher spatial resolution noticeably helps to improve the radiation results. We present a new Monte Carlo model, MoCaRT, that computes the radiative transfer in three-dimensional inhomogeneous atmospheres. The MoCaRT model is validated by comparison with the consensus results of the Intercomparison of Three-Dimensional Radiation Codes (I3RC) project. In the framework of this paper, we aim at characterising cloud heterogeneity effects on radiances and broadband fluxes, namely: the errors due to unresolved variability (the so-called plane parallel homogeneous, PPH, bias) and the errors due to the neglect of transversal photon displacements (independent pixel approximation, IPA, bias). First, we study the effect of the missing cloud variability on reflectivities. We will show that the generation of subscale variability by means of stochastic methods greatly reduce or nearly eliminate the reflectivity biases. Secondly, three-dimensional broadband fluxes in the presence of realistic inhomogeneous cloud fields sampled at high spatial resolutions are calculated and compared to their one-dimensional counterparts at coarser resolutions. We found that one-dimensional calculations at coarsely resolved cloudy atmospheres systematically overestimate broadband reflected and absorbed fluxes and underestimate transmitted ones.

scholarly journals Analysis of the Discrete Theory of Radiative Transfer in the Coupled “Ocean–Atmosphere” System: Current Status, Problems and Development Prospects

2020 ◽  
Vol 8 (3) ◽  
pp. 202 ◽  
Author(s):  
Viktor P. Afanas’ev ◽  
Alexander Yu. Basov ◽  
Vladimir P. Budak ◽  
Dmitry S. Efremenko ◽  
Alexander A. Kokhanovsky
Keyword(s):  
Radiative Transfer ◽  
Three Dimensional ◽  
Operator Method ◽  
Current Status ◽  
One Dimensional ◽  
Current State ◽  
The Matrix ◽  
The One ◽  
Discrete Theory ◽  
Development Prospects

In this paper, we analyze the current state of the discrete theory of radiative transfer. One-dimensional, three-dimensional and stochastic radiative transfer models are considered. It is shown that the discrete theory provides a unique solution to the one-dimensional radiative transfer equation. All approximate solution techniques based on the discrete ordinate formalism can be derived based on the synthetic iterations, the small-angle approximation, and the matrix operator method. The possible directions for the perspective development of radiative transfer are outlined.

Resistance of superconducting-normal interfaces at 0 K

1984 ◽  
Vol 391 (1801) ◽  
pp. 255-268 ◽  
Keyword(s):  
Radiative Transfer ◽  
Dimensional Analysis ◽  
Andreev Reflection ◽  
Three Dimensional ◽  
Linear Variation ◽  
Dimensional Theory ◽  
Milne Problem ◽  
One Dimensional ◽  
Interface Resistance ◽  
Bismuth Content

The model proposed by G. L. Harding, A. B. Pippard and J. R. Tomlinson (Harding, Pippard & Tomlinson, Proc . R . Soc . Lond . A340, 1 (1974)) to explain their observation of an enhanced interface resistance at a junction of copper and lead, when bismuth is added to the lead, is developed into a more satisfactory three-dimensional theory. The model for the resistance at 0 K is shown to resemble the Milne problem in radiative transfer, as treated by Chandrasekhar, but considerably modified by Andreev reflection. The theory predicts a linear variation of resistance with bismuth content, as is not incompatible with the measurements, but the magnitude of the calculated resistance, though considerably less than what was found in the original one-dimensional analysis, is still at least 50 % too high. Factors are suggested that should be taken into account in a thorough treatment of the interface, but without any assurance that they would eliminate the discrepancy.

2,3-Dihydro-7,8-dihydroxy-3-[(4-methoxyphenyl)methylene]-4H-1-benzopyran-4-one

2006 ◽  
Vol 62 (4) ◽  
pp. o1254-o1256 ◽  
Author(s):  
Suchada Chantrapromma ◽  
Sompong Boonsri ◽  
Hoong-Kun Fun ◽  
Shazia Anjum ◽  
Akkharawit Kanjana-opas
Keyword(s):  
Hydrogen Bonds ◽  
Intermolecular Interactions ◽  
Title Compound ◽  
Three Dimensional ◽  
Molecular Network ◽  
Pyran Ring ◽  
Intramolecular Hydrogen Bonds ◽  
One Dimensional ◽  
Intramolecular Hydrogen ◽  
First Time

The title compound, also known as intricatinol, C17H14O5, is a homoisoflavanoid that was isolated for the first time from the twigs and stems of Caesalpinia digyna Rottler. The pyran ring is in an envelope form. O—H...O intramolecular hydrogen bonds are observed. Symmetry-related molecules are linked via O—H...O intermolecular interactions to form infinite one-dimensional chains. These chains are interconnected to form a three-dimensional molecular network.

Transient Radiation Element Method for Three-Dimensional Scattering, Absorbing, and Emitting Media

2001 ◽  
Author(s):  
Zhixiong Guo ◽  
Sunil Kumar ◽  
Shigenao Maruyama
Keyword(s):  
Radiative Transfer ◽  
Transient Analysis ◽  
Radiative Heat ◽  
Three Dimensional ◽  
The Media ◽  
Emitting Media ◽  
Inhomogeneous Properties ◽  
First Time ◽  
Good Agreement ◽  
Element Method

Abstract In this study transient radiative heat transfer is investigated in scattering, absorbing, and emitting media. The radiation element method is formulated for the first time to solve the transient radiative transfer equation in 3-D geometries. The sensitivity and accuracy of the method are examined. A good agreement of temporal transmittance predicted by the present method and Monte Carlo method is found. The characteristics of transient analysis are investigated via various problems of radiative transfer in inhomogeneous cubes. It is found that the transmitted signals are strongly affected by the inhomogeneous properties of the media through which the radiation has passed. In the position where the radiation travels a larger optical thickness, the broadening of the transmitted pulse width is more obvious and the magnitude of the transmittance is smaller.

scholarly journals The wave-induced flow of internal gravity wavepackets with arbitrary aspect ratio

2017 ◽  
Vol 834 ◽  
pp. 385-408 ◽  
Author(s):  
T. S. van den Bremer ◽  
B. R. Sutherland
Keyword(s):  
Aspect Ratio ◽  
Three Dimensional ◽  
Mean Flow ◽  
One Dimensional ◽  
Unidirectional Flow ◽  
Aspect Ratios ◽  
Non Local ◽  
Flow Through ◽  
Induced Flow ◽  
Wave Induced

We examine the wave-induced flow of small-amplitude, quasi-monochromatic, three-dimensional, Boussinesq internal gravity wavepackets in a uniformly stratified ambient. It has been known since Bretherton (J. Fluid Mech., vol. 36 (4), 1969, pp. 785–803) that one-, two- and three-dimensional wavepackets induce qualitatively different flows. Whereas the wave-induced mean flow for compact three-dimensional wavepackets consists of a purely horizontal localized circulation that translates with and around the wavepacket, known as the Bretherton flow, such a flow is prohibited for a two-dimensional wavepacket of infinite spanwise extent, which instead induces a non-local internal wave response that is long compared with the streamwise extent of the wavepacket. One-dimensional (horizontally periodic) wavepackets induce a horizontal, non-divergent unidirectional flow. Through perturbation theory for quasi-monochromatic wavepackets of arbitrary aspect ratio, we predict for which aspect ratios which type of induced mean flow dominates. We compose a regime diagram that delineates whether the induced flow is comparable to that of one-, two- or compact three-dimensional wavepackets. The predictions agree well with the results of fully nonlinear three-dimensional numerical simulations.

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