Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.stsci.edu/~valenti/sme/SME_tutorial.pdf Дата изменения: Mon Oct 1 01:01:06 2012 Дата индексирования: Sat Mar 1 23:59:49 2014 Кодировка: Поисковые слова: п п п п п п п п п п п п п п п п п п п п п п п п п п п п п п п п п п п п п п

SME tutorial
January 31 ­ February 2, 2011 Uppsala


Schedule
Monday
Short intro to SME Installation and testing of the installation


Tuesday
3 exercises (creating SME input structure, solving of global parameters, tuning line parameters) Starting to work on your data



SME physics




SME (= Spectroscopy Made Easy) computes spectral synthesis and adjusts free parameters based on comparison with obser vations SME spectral synthesis consists of molecular and ionization equilibrium solver EOS, continuous opacity package CONTOP, line opacity package LINEOP and RT solver RTINT


EOS





Abundances Zatom is the ratio natom / ntotal Sc X Apoemies is the number of particular t atoms in a particular species H H (e.g. X H O 2, X C O 0) X Species is the total number of atoms in a particular species (e.g. X H O 3)
2 2
2

q

species

charge of a given species: q

TiO+ H

1 1

q


Abundance and conser vation equations


Abundances (X is the number of atoms in a Sp c given species): nspecies X Atoemies
Z
Atom



species

species



nspecies X

Species



Total number of particles:
ne
species



nspecies ntotal P kT



Charge conser vation (q is the electric charge):
species



nspecies q

species

ne


Chemistry


Chemical reaction in which species A and B form AB can be described by the chemical equilibrium equation: 3 3 D 2 2 AB nA nB 2 kT mAmB U AU B K (T ) 2 e kT nAB h mAB U AB Ionization can be described in exact same way:
nA ne n
A



2 me kT 2U K (T ) h2 U

3 2

A A

e



IA kT

Saha equation!


Using EOS








EOS has partition functions for 6 ionization stages of the first 99 atoms in the periodic table EOS has partition functions for 257 molecules (up to four atoms) fitted over the range from 10K to 8000K Input consists of T, P and abundances. Pe can be also imposed EOS is using rather unique solving strategy making it robust


CONTOP







Continuous opacities are from ATLAS12 Modifications: partial pressures of absorbers and their partition functions are taken from EOS List of absorbers: H, H2+, H-, He, He+, He-, Si, Si+, Mg, Mg+, Al, C, Fe, Ca+, N, O, Ne, S, List of scatterers: H, H2, He, e-


LINEOP








Given partial number densities of the line absorbers and their partition functions computes line opacities Voigt profiles except for hydrogen lines Natural, Stark and van der Waals broadening Two-parameter van der Waals broadening (Anstee, Barklem & O'Mara, http://www.astro.uu.se/~barklem/howto.html) Hydrogen lines are computed using Barklem and Piskunov code HLINOP (http://www.astro.uu.se/~barklem/hlinop.html) taking into account self broadening and other effects. Stark broadening and Stark shift are explicitly computed for the lines of neutral helium.


RTINT






Single pass short-characteristics algorithm developed for 3D radiative transfer code: fast and robust even on a sparse grid. Attenuation operator with quadratic Bezier spline approximation to the source function Bezier spline prevents overshooting


RTINT: equations
RT equation: = - Formal solution: I ( i 1 ) e ( i1

i )

I ( i )
(
i 1






i

i 1

S (t ) e

t )

dt

Approximation to the source function:
+1

2 + + for

Attenuation operator :
+1



=

-

+

-1

+ +

+1


RTINT: Bezier spline


SME implementation




SME consists of two independent parts: GUI and solver Solver consists of the IDL routines for preparing spectral synthesis and performing optimization and an external library for computing synthetic spectra GUI let you prepare data for the solver and interpret the results but there at least two other packages to do it noninteractively


Solver




Spectral synthesis requires various data: line list, wavelength range, atmospheric model(s), initial parameters. All of this (except when model interpolation is required) are collected in one structure ­ the so-called input structure Solver takes the input structure and performs its tasks and saves the results into an output structure. Both input and output structures have name sme Once the input structure is prepared you can run solver manually:
restore,'input_sme.sav' sme_main,sme save,sme,file=`output_sme.sav'


Solver


You can also examine the sme structure in your idl session:
help,sme,/str

The external library is written in C++ and Fortran and it has about ten entry points. Conventionally the library should be located in the same place where sme_main.pro is and must be called sme_synth.so. Normally one would create a link with this name to the correct library. This are used in particular sequence: setting wavelength range, passing atmospheric model, passing line list, solving for molecular-ionization equilibrium, performing spectral synthesis etc. Things computed within the library with each call are stored in separate memory and can be prompted from IDL using the corresponding calls.



GUI




GUI is interactive tool for creating input structures and examining the output structures GUI includes tools for importing line lists in VALD format, for importing observations, setting abundances, selecting atmospheric model(s), free parameters etc. When you save the results of GUI setup, it will automatically create an input structure! GUI can also read both input and output structures. GUI also has a graphics tool to show the results.