Radiation Parameters
~~~~~~~~~~~~~~~~~~~~
.. _radiation_backgrounds:
Background Radiation Parameters
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
``RadiationFieldType`` (external)
This integer parameter specifies the type of radiation field that
is to be used. Except for ``RadiationFieldType`` = 9, which should
be used with ``MultiSpecies`` = 2, UV backgrounds can currently
only be used with ``MultiSpecies`` = 1 (i.e. no molecular H
support). The following values are used. For field type 15, see
Table 3 in `Haardt & Madau (2012)
`_. Default: 0
::
1 - Haardt & Madau spectrum with q_alpha = 1.5
2 - Haardt & Madau spectrum with q_alpha = 1.8
3 - Modified Haardt & Madau spectrum to match observations
(Kirkman & Tytler 2005).
4 - Haardt & Madau spectrum with q_alpha = 1.5 supplemented with an X-ray Compton heating
background from Madau & Efstathiou (see astro-ph/9902080)
9 - Constant molecular H2 photo-dissociation rate
10 - Internally computed radiation field using the algorithm of Cen & Ostriker
11 - Same as previous, but with very, very simple optical shielding fudge
12 - Haardt & Madau spectrum with q_alpha = 1.57
15 - Haardt & Madau 2012.
``RadiationFieldLevelRecompute`` (external)
This integer parameter is used only if the previous parameter is
set to 10 or 11. It controls how often (i.e. the level at which)
the internal radiation field is recomputed. Default: 0
``RadiationSpectrumNormalization`` (external)
This parameter was initially used to normalize the photo-ionization
and photo-heating rates computed in the function
``RadiationFieldCalculateRates()`` and then passed on to the
``calc_photo_rates()``, ``calc_rad()`` and ``calc_rates()`` routines.
Later, the normalization as a separate input parameter was dropped
for all cases by using the rates computed in
``RadiationFieldCalculateRates()`` with one exception: The molecular
hydrogen (H2) dissociation rate. There a normalization is performed
on the rate by multiplying it with ``RadiationSpectrumNormalization``.
Default: 1e-21
``RadiationShield`` (external)
This parameter specifies whether the user wants to employ
approximate radiative-shielding. This parameter will be
automatically turned on when RadiationFieldType is set to 11. When
set to 1, it calculates shielding for H/He. See
``calc_photo_rates.src`` for more details. When set to 2, it
shields only H2 with the Sobolev-like approximation from
Wolcott-Green et al. (2011). Default: 0
``RadiationFieldRedshift`` (external)
This parameter specifies the redshift at which the radiation field
is calculated. If a UV radiation background is used in a
non-cosmological simulation, this needs to be defined. Default:
(undefined)
``RadiationRedshiftOn`` (external)
The redshift at which the UV
background turns on. Default: 7.0.
``RadiationRedshiftFullOn`` (external)
The redshift at which the UV
background is at full strength. Between z =
``RadiationRedshiftOn`` and z = ``RadiationRedshiftFullOn``, the
background is gradually ramped up to full strength. Default: 6.0.
``RadiationRedshiftDropOff`` (external)
The redshift at which the
strength of the UV background is begins to gradually reduce,
reaching zero by ``RadiationRedshiftOff``. Default: 0.0.
``RadiationRedshiftOff`` (external)
The redshift at which the UV
background is fully off. Default: 0.0.
``TabulatedLWBackground`` (external)
When on, the amplitude of the Lyman-Werner background is read from the file LW_J21.in as a function of redshift. Each line should have the redshift and LW background in units of 1e-21 erg/cm^3/s/Hz/sr. Default: 0
``AdjustUVBackground`` (external)
Add description. Default: 1.
``AdjustUVBackgroundHighRedshift`` (external)
Add description. Default: 0.
``SetUVAmplitude`` (external)
Add description. Default: 1.0.
``SetHeIIHeatingScale`` (external)
Add description. Default: 1.8.
``RadiationSpectrumSlope`` (external)
Add description. Default: 1.5.
.. _radiative_transfer_ray_tracing:
Radiative Transfer (Ray Tracing) Parameters
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
``RadiativeTransfer`` (external)
Set to 1 to turn on the adaptive ray tracing following Abel, Wise &
Bryan 2007. Note that Enzo must be first recompiled after setting
``make photon-yes``. Default: 0.
``RadiativeTransferRadiationPressure`` (external)
Set to 1 to turn on radiation pressure created from absorbed photon
packages. Default: 0
``RadiativeTransferInitialHEALPixLevel`` (external)
Chooses how many rays are emitted from radiation sources. The
number of rays in Healpix are given through # =
12x4\ :sup:`level`\ . Default: 3.
``RadiativeTransferRaysPerCell`` (external)
Determines the accuracy of the scheme by giving the minimum number
of rays to cross cells. The more the better (slower). Default: 5.1.
``RadiativeTransferSourceRadius`` (external)
The radius at which the photons originate from the radiation
source. A positive value results in a radiating sphere. Default: 0.
``RadiativeTransferPropagationRadius`` (external)
The maximum distance a photon package can travel in one timestep.
Currently unused. Default: 0.
``RadiativeTransferPropagationSpeed`` (external)
The fraction of the speed of light at which the photons travel.
Default: 1.
``RadiativeTransferCoupledRateSolver`` (external)
Set to 1 to calculate the new ionization fractions and gas energies
after every radiative transfer timestep. This option is highly
recommended to be kept on. If not, ionization fronts will propagate too
slowly. Default: 1.
``RadiativeTransferOpticallyThinH2`` (external)
Set to 1 to include an optically-thin H_2 dissociating
(Lyman-Werner) radiation field. Only used if ``MultiSpecies`` > 1. If
``MultiSpecies`` > 1 and this option is off, the Lyman-Werner radiation
field will be calculated with ray tracing. Default: 1.
``RadiativeTransferSplitPhotonPackage`` (external)
Once photons are past this radius, they can no longer split. In
units of kpc. If this value is negative (by default), photons can
always split. Default: ``FLOAT_UNDEFINED``.
``RadiativeTransferHubbleTimeFraction`` (external)
Photon packages are deleted when its associated photo-ionization
timescale, considering the limit when all photons are absorbed in
one cell, drops below a fraction (this parameter) of a Hubble
time. This parameter can be safely set to 0.01 when ray merging
is used. Default: 0.1
``RadiativeTransferFluxBackgroundLimit`` (external)
When the flux of a photon package drops below a fraction (this
parameter) of the background radiation field, the ray is deleted.
Only used with ray merging. Default: 0.01
``RadiativeTransferPhotonEscapeRadius`` (external)
The number of photons that pass this distance from its source are
summed into the global variable ``EscapedPhotonCount[]``. This variable
also keeps track of the number of photons passing this radius
multiplied by 0.5, 1, and 2. Units are in kpc. Not used if set to
0. Default: 0.
``RadiativeTransferSourceClustering`` (external)
Set to 1 to turn on ray merging from combined virtual sources on a
binary tree. Default: 0.
``RadiativeTransferPhotonMergeRadius`` (external)
The radius at which the rays will merge from their SuperSource,
which is the luminosity weighted center of two sources. This radius
is in units of the separation of two sources associated with one
SuperSource. If set too small, there will be angular artifacts in
the radiation field. Default: 2.5
``RadiativeTransferSourceBeamAngle`` (external)
Rays will be emitted within this angle in degrees of the poles from sources with "Beamed" types. Default: 30
``RadiativeTransferPeriodicBoundary`` (external)
Set to 1 to turn on periodic boundary conditions for photon
packages. Default: 0.
``RadiativeTransferTimestepVelocityLimit`` (external)
Limits the radiative transfer timestep to a minimum value that is
determined by the cell width at the finest level divided by this
velocity. Units are in km/s. Default: 100.
``RadiativeTransferTimestepVelocityLevel`` (external)
Limit the ray tracing timestep by a sound crossing time (see
``RadiativeTransferTimestepVelocityLimit``) across a
cell on the level specified with this parameter. Not used if
equal to INT_UNDEFINED (-99999). Default: INT_UNDEFINED
``RadiativeTransferHIIRestrictedTimestep`` (external)
Adaptive ray tracing timesteps will be restricted by a maximum change of 10% in neutral fraction if this parameter is set to 1. If set to 2, then the incident flux can change by a maximum of 0.5 between cells. See Wise & Abel (2011) in Sections 3.4.1 and 3.4.4 for more details. Default: 0
``RadiativeTransferAdaptiveTimestep`` (external)
Must be 1 when RadiativeTransferHIIRestrictedTimestep is non-zero. When RadiativeTransferHIIRestrictedTimestep is 0, then the radiative transfer timestep is set to the timestep of the finest AMR level. Default: 0
``RadiativeTransferLoadBalance`` (external)
When turned on, the grids are load balanced based on the number of ray segments traced. The grids are moved to different processors only for the radiative transfer solver. Default: 0
``RadiativeTransferHydrogenOnly`` (external)
When turned on, the photo-ionization fields are only created for hydrogen. Default: 0
``RadiationXRaySecondaryIon`` (external)
Set to 1 to turn on secondary ionizations and reduce heating from
X-ray radiation (Shull & van Steenberg 1985). Currently only BH and
MBH particles emit X-rays. Default: 0.
``RadiationXRayComptonHeating`` (external)
Set to 1 to turn on Compton heating on electrons from X-ray
radiation (Ciotti & Ostriker 2001). Currently only BH and MBH
particles emit X-rays. Default: 0.
``RadiativeTransferInterpolateField`` (obsolete)
A failed experiment in which we evaluate the density at the
midpoint of the ray segment in each cell to calculate the optical
depth. To interpolate, we need to calculate the vertex interpolated
density fields. Default: 0.
``SimpleQ`` (external)
Ionizing photon luminosity of a "simple radiating source" that is independent of mass. In units of photons per second. Default: 1e50
``SimpleRampTime`` (external)
Time to exponential ramp up the luminosity of a simple radiating source. In units of 1e6 years. Default: 0.1
``RadiativeTransferTraceSpectrum`` (reserved)
reserved for future experimentation. Default: 0.
``RadiativeTransferTraceSpectrumTable`` (reserved)
reserved for future experimentation. Default: ``spectrum_table.dat``
.. _radiative_transfer_fld:
Radiative Transfer (FLD) Parameters
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
``RadiativeTransferFLD`` (external)
Set to 2 to turn on the fld-based radiation solvers following Reynolds,
Hayes, Paschos & Norman, 2009. Note that you also have to compile
the source using ``make photon-yes`` and a ``make
hypre-yes``. Note that if FLD is turned on, it will force
``RadiativeCooling = 0``, ``GadgetEquilibriumCooling = 0``, and
``RadiationFieldType = 0`` to prevent conflicts. Default: 0.
*IMPORTANT*: Set ``RadiativeTransfer = 0`` to avoid conflicts with the ray tracing solver above.
Set ``RadiativeTransferOpticallyThinH2 = 0`` to avoid conflicts with the built-in optically-thin H_2 dissociating field from the ray-tracing solver.
``ImplicitProblem`` (external)
Set to 1 to turn on the implicit FLD solver, or 3 to turn on the
split FLD solver. Default: 0.
``RadHydroParamfile`` (external)
Names the (possibly-different) input parameter file containing
solver options for the FLD-based solvers. These are described in
the relevant User Guides, located in ``doc/implicit_fld`` and
``doc/split_fld``. Default: NULL.
``RadiativeTransferFLDCallOnLevel`` (reserved)
The level in the static AMR hierarchy where the unigrid FLD solver
should be called. Currently only works for 0 (the root grid).
Default: 0.
``StarMakerEmissivityField`` (external)
When compiled with the FLD radiation transfer >make emissivity-yes; make hypre-yes, setting this to 1 turns on the emissivity field to source the gray radiation. Default: 0
``uv_param`` (external)
When using the FLD radiation transfer and StarMakerEmissivityFIeld = 1, this is the efficiency of mass to UV light ratio. Default: 0
Radiative Transfer (FLD) Implicit Solver Parameters
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
These parameters should be placed within the file named in
``RadHydroParamfile`` in the main parameter file. All are described in
detail in the User Guide in ``doc/implicit_fld``.
``RadHydroESpectrum`` (external)
Type of assumed radiation spectrum for radiation field, Default: 1.
::
-1 - monochromatic spectrum at frequency h nu_{HI} = 13.6 eV
0 - power law spectrum, (nu / nu_{HI} )^(-1.5)
1 - T = 1e5 blackbody spectrum
``RadHydroChemistry`` (external)
Use of hydrogen chemistry in ionization model, set to 1 to turn on
the hydrogen chemistry, 0 otherwise. Default: 1.
``RadHydroHFraction`` (external)
Fraction of baryonic matter comprised of hydrogen. Default: 1.0.
``RadHydroModel`` (external)
Determines which set of equations to use within the solver.
Default: 1.
::
1 - chemistry-dependent model, with case-B hydrogen II recombination coefficient.
2 - chemistry-dependent model, with case-A hydrogen II recombination coefficient.
4 - chemistry-dependent model, with case-A hydrogen II
recombination coefficient, but assumes an isothermal gas energy.
10 - no chemistry, instead uses a model of local thermodynamic
equilibrium to couple radiation to gas energy.
``RadHydroMaxDt`` (external)
maximum time step to use in the FLD solver. Default: 1e20 (no
limit).
``RadHydroMinDt`` (external)
minimum time step to use in the FLD solver. Default: 0.0 (no
limit).
``RadHydroInitDt`` (external)
initial time step to use in the FLD solver. Default: 1e20 (uses
hydro time step).
``RadHydroDtNorm`` (external)
type of p-norm to use in estimating time-accuracy for predicting
next time step. Default: 2.0.
::
0 - use the max-norm.
>0 - use the specified p-norm.
<0 - illegal.
``RadHydroDtRadFac`` (external)
Desired time accuracy tolerance for the radiation field. Default:
1e20 (unused).
``RadHydroDtGasFac`` (external)
Desired time accuracy tolerance for the gas energy field. Default:
1e20 (unused).
``RadHydroDtChemFac`` (external)
Desired time accuracy tolerance for the hydrogen I number density.
Default: 1e20 (unused).
``RadiationScaling`` (external)
Scaling factor for the radiation field, in case standard
non-dimensionalization fails. Default: 1.0.
``EnergyCorrectionScaling`` (external)
Scaling factor for the gas energy correction, in case standard
non-dimensionalization fails. Default: 1.0.
``ChemistryScaling`` (external)
Scaling factor for the hydrogen I number density, in case standard
non-dimensionalization fails. Default: 1.0.
``RadiationBoundaryX0Faces`` (external)
Boundary condition types to use on the x0 faces of the radiation
field. Default: [0 0].
::
0 - Periodic.
1 - Dirichlet.
2 - Neumann.
``RadiationBoundaryX1Faces`` (external)
Boundary condition types to use on the x1 faces of the radiation
field. Default: [0 0].
``RadiationBoundaryX2Faces`` (external)
Boundary condition types to use on the x2 faces of the radiation
field. Default: [0 0].
``RadHydroLimiterType`` (external)
Type of flux limiter to use in the FLD approximation. Default: 4.
::
0 - original Levermore-Pomraning limiter, à la Levermore & Pomraning, 1981 and Levermore, 1984.
1 - rational approximation to LP limiter.
2 - new approximation to LP limiter (to reduce floating-point cancellation error).
3 - no limiter.
4 - ZEUS limiter (limiter 2, but with no "effective albedo").
``RadHydroTheta`` (external)
Time-discretization parameter to use, 0 gives explicit Euler, 1
gives implicit Euler, 0.5 gives trapezoidal. Default: 1.0.
``RadHydroAnalyticChem`` (external)
Type of time approximation to use on gas energy and chemistry
equations. Default: 1 (if possible for model).
::
0 - use a standard theta-method.
1 - use an implicit quasi-steady state (IQSS) approximation.
``RadHydroInitialGuess`` (external)
Type of algorithm to use in computing the initial guess for the
time-evolved solution. Default: 0.
::
0 - use the solution from the previous time step (safest).
1 - use explicit Euler with only spatially-local physics (heating & cooling).
2 - use explicit Euler with all physics.
5 - use an analytic predictor based on IQSS approximation of
spatially-local physics.
``RadHydroNewtTolerance`` (external)
Desired accuracy for solution to satisfy nonlinear residual
(measured in the RMS norm). Default: 1e-6.
``RadHydroNewtIters`` (external)
Allowed number of Inexact Newton iterations to achieve tolerance
before returning with FAIL. Default: 20.
``RadHydroINConst`` (external)
Inexact Newton constant used in specifying tolerances for inner
linear solver. Default: 1e-8.
``RadHydroMaxMGIters`` (external)
Allowed number of iterations for the inner linear solver (geometric
multigrid). Default: 50.
``RadHydroMGRelaxType`` (external)
Relaxation method used by the multigrid solver. Default: 1.
::
1 - Jacobi.
2 - Weighted Jacobi.
3 - Red/Black Gauss-Seidel (symmetric).
4 - Red/Black Gauss-Seidel (non-symmetric).
``RadHydroMGPreRelax`` (external)
Number of pre-relaxation sweeps used by the multigrid solver.
Default: 1.
``RadHydroMGPostRelax`` (external)
Number of post-relaxation sweeps used by the multigrid solver.
Default: 1.
``EnergyOpacityC0``, ``EnergyOpacityC1``, ``EnergyOpacityC2``, ``EnergyOpacityC3``, ``EnergyOpacityC4`` (external)
Parameters used in defining the energy-mean opacity used with
``RadHydroModel`` 10. Default: [1 1 0 1 0].
``PlanckOpacityC0``, ``PlanckOpacityC1``, ``PlanckOpacityC2``, ``PlanckOpacityC3``, ``PlanckOpacityC4`` (external)
Parameters used in defining the Planck-mean opacity used with
``RadHydroModel`` 10. Default: [1 1 0 1 0].
Radiative Transfer (FLD) Split Solver Parameters
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
These parameters should be placed within the file named in
``RadHydroParamfile`` in the main parameter file. All are described in
detail in the User Guide in ``doc/split_fld``.
``RadHydroESpectrum`` (external)
Type of assumed radiation spectrum for radiation field, Default: 1.
::
1 - T=1e5 blackbody spectrum
0 - power law spectrum, ( nu / nu_{HI})^(-1.5)`
-1 - monochromatic spectrum at frequency h nu_{HI}= 13.6 eV
-2 - monochromatic spectrum at frequency h nu_{HeI}= 24.6 eV
-3 - monochromatic spectrum at frequency h nu_{HeII}= 54.4 eV
``RadHydroChemistry`` (external)
Use of primordial chemistry in computing opacities and
photo-heating/photo-ionization. Default: 1.
::
0 no chemistry
1 hydrogen chemistry
3 hydrogen and helium chemistry
``RadHydroHFraction`` (external)
Fraction of baryonic matter comprised of hydrogen. Default: 1.0.
``RadHydroModel`` (external)
Determines which set of equations to use within the solver.
Default: 1.
::
1 - chemistry-dependent model, with case-B hydrogen II recombination
coefficient.
4 - chemistry-dependent model, with case-A hydrogen II recombination
coefficient, but assumes an isothermal gas energy.
10 - no chemistry, instead uses a model of local thermodynamic
equilibrium to couple radiation to gas energy.
``RadHydroMaxDt`` (external)
maximum time step to use in the FLD solver. Default: 1e20 (no
limit).
``RadHydroMinDt`` (external)
minimum time step to use in the FLD solver. Default: 0.0 (no
limit).
``RadHydroInitDt`` (external)
initial time step to use in the FLD solver. Default: 1e20 (uses
hydro time step).
``RadHydroMaxSubcycles`` (external)
desired number of FLD time steps per hydrodynamics time step (must
be greater than or equal to 1). This is only recommended if the
FLD solver is performing chemistry and heating internally, since
it will only synchronize with the ionization state at each
hydrodynamic time step. When using Enzo's chemistry and cooling
solvers this parameter should be set to 1 to avoid overly
decoupling radiation and chemistry. Default: 1.0.
``RadHydroMaxChemSubcycles`` (external)
desired number of chemistry time steps per FLD time step. This
only applies if the FLD solver is performing chemistry and heating
internally, instead of using Enzo's built-in routines for this
task. Default: 1.0.
``RadHydroDtNorm`` (external)
type of p-norm to use in estimating time-accuracy for predicting
next time step. Default: 2.0.
::
0 - use the max-norm.
>0 - use the specified p-norm.
<0 - illegal.
``RadHydroDtGrowth`` (external)
Maximum growth factor in the FLD time step between successive
iterations. Default: 1.1 (10% growth).
``RadHydroDtRadFac`` (external)
Desired time accuracy tolerance for the radiation field. Default:
1e20 (unused).
``RadHydroDtGasFac`` (external)
Desired time accuracy tolerance for the gas energy field. Only
used if the FLD solver is performing heating internally. Default:
1e20 (unused).
``RadHydroDtChemFac`` (external)
Desired time accuracy tolerance for the hydrogen I number
density. Only used if the FLD solver is performing chemistry
internally. Default: 1e20 (unused).
``RadiationScaling`` (external)
Scaling factor for the radiation field, in case standard
non-dimensionalization fails. Default: 1.0.
``EnergyCorrectionScaling`` (external)
Scaling factor for the gas energy correction, in case standard
non-dimensionalization fails. Default: 1.0.
``ChemistryScaling`` (external)
Scaling factor for the hydrogen I number density, in case standard
non-dimensionalization fails. Default: 1.0.
``AutomaticScaling`` (external)
Enables an heuristic approach in the FLD solver to update the
above scaling factors internally. Works well for reioniztaion
calculations, but is not recommended for problems in which the
optimal unit scaling factor is known a-priori. Default: 1.0.
``RadiationBoundaryX0Faces`` (external)
Boundary condition types to use on the x0 faces of the radiation
field. Default: [0 0].
::
0 - Periodic.
1 - Dirichlet.
2 - Neumann.
``RadiationBoundaryX1Faces`` (external)
Boundary condition types to use on the x1 faces of the radiation
field. Default: [0 0].
``RadiationBoundaryX2Faces`` (external)
Boundary condition types to use on the x2 faces of the radiation
field. Default: [0 0].
``RadHydroTheta`` (external)
Time-discretization parameter to use, 0 gives explicit Euler, 1
gives implicit Euler, 0.5 gives trapezoidal. Default: 1.0.
``RadHydroKrylovMethod`` (external)
Desired outer linear solver algorithm to use. Default: 1.
::
0 - Preconditioned Conjugate Gradient (PCG)
1 - Stabilized Bi-Conjugate Gradient (BiCGStab)
2 - Generalized Minimum Residual (GMRES)
``RadHydroSolTolerance`` (external)
Desired accuracy for solution to satisfy linear residual (measured
in the 2-norm). Default: 1e-8.
``RadHydroMaxMGIters`` (external)
Allowed number of iterations for the inner linear solver (geometric
multigrid). Default: 50.
``RadHydroMGRelaxType`` (external)
Relaxation method used by the multigrid solver. Default: 1.
::
0 - Jacobi
1 - Weighted Jacobi
2 - Red/Black Gauss-Seidel (symmetric)
3 - Red/Black Gauss-Seidel (non-symmetric)
``RadHydroMGPreRelax`` (external)
Number of pre-relaxation sweeps used by the multigrid solver.
Default: 1.
``RadHydroMGPostRelax`` (external)
Number of post-relaxation sweeps used by the multigrid solver.
Default: 1.
``EnergyOpacityC0``, ``EnergyOpacityC1``, ``EnergyOpacityC2`` (external)
Parameters used in defining the energy-mean opacity used with
RadHydroModel 10. Default: [1 1 0].