Introduction

This page lists every gs2 input parameter currently known about, along with any help available. It is intended as a reference, not an introduction. Note: some parameters are highly specialised and not intended for general use.

A full introduction to writing input files is to be written, but until then, this is an old example input file. Be aware that not every section should be included.

Format

The parameters are divided into namelists. Each parameter has type information and written help where available. The format is:

Name Type Def CR Name Description
Name as it appears in gs2 Fortran Data Type Autoscanned Default(s): guesses at what the default value of this parameter will be if you do not specify it in the input file. They are usually correct. CodeRunner Name: is the variable name used by CodeRunner to refer to the quantity (only given if it is different to the gs2 name).

Long and detailed help for the variable

This page is automatically generated by CodeRunner, but any changes you make will be kept, so please feel free to contribute. Please keep to the same format as this allows easy automatic syncing of your changes with the CodeRunner database. Please only edit in between the <!-- begin help --> <!-- end help --> or the <!-- begin namelist help --> <!-- end namelist help --> tags. Don't edit type/default information (or this introduction) as it will not be kept.

Namelists

Each gs2 module is controlled by its own namelist. For typical applications, not all 32+ namelists should appear in a single file. For a run called runname, this file should be called runname.in. In most cases, defaults are loaded for each namelist element, so that if a namelist or element does not appear, the run will not automatically stop. (It may still be forced to stop if the defaults are incompatible with your other choices.) The namelists and defaults appear below.

parameters

Name Type Def CR Name Description
beta Float 0.0 beta
• In GS2 $\beta$ is the ratio of the reference pressure to the reference magnetic energy density, $\beta = 2 \mu_0 n_{\rm ref} T_{\rm ref}/B_{\rm ref}^2$. Mainly GS2 uses $\beta$ to determine the amplitude of the perturbed magnetic fields.
• For electromagnetic runs, the contribution of each species to the total parallel current is weighted by a factor of $w_s = 2 \beta Z_s n_s \sqrt{T_s/m_s}$.
• Handy formula: 403. * nref_19 * T_ref(kev) / 1.e5 / B_T**2, where nref_19 is the reference density / 10**19 and B_T is the magnetic field in Tesla.
• For electromagnetic runs that include $\delta B_\parallel$, this field is proportional to $\beta$.
• The contribution of $(\delta B)^2$ to the total gyrokinetic energy is inversely proportional to this input parameter.
• If an antenna is set up to drive Alfven waves, then $\beta$ is used to calculate the Alfven frequency.
• For some collision operator models, $\beta$ is used to calculate the resistivity.
• For some rarely-used initial conditions, $\beta$ appears explicitly.
• Important: $\beta$ is not a GS2 plasma equilibrium parameter, but it must be chosen with care. $\beta$ is not automatically consistent with the value of $\beta'$ used in the local magnetic equilibrium. The user is responsible for ensuring that the values of $\beta$ together with the densities, temperatures and gradients for all species are consistent with the local equilibrium value of $\beta'$.
k0 Float 1.0 parameters_k0
rhostar Float 0.003 rhostar
• Normalised gyro-radius, $\frac{\rho}{a}$, needed for calculating the momentum flux in the low flow limit.
teti Float -100.0 teti
• Ratio of electron to ion temperatures. Deprecated. Do not use unless you know what you are doing.
tite Float 1.0 tite
• Ratio of ion to electron temperatures. This parameter is used only when there is no species called "electron" included.
zeff Float 1.0 zeff
• Effective ionic charge. The parameter $Z_{\rm eff}$ appears only in the electron collision frequency, and is not automatically set to be consistent with the mix of species specified in the species namelists.

kt_grids_knobs

There are two variables which may be determined at the highest level of the kt_grids module: grid_option and norm_option. The first determines which Fourier modes perpendicular to the field lines will be evolved in time. For each possible choice, there is a subsidiary module (and namelist) which controls the details. The norm_option variable simply fixes the definition of the thermal velocity.

Name Type Def CR Name Description
grid_option String default grid_option

kt_grids_box_parameters

Name Type Def CR Name Description
jtwist Integer jtwist
• For finite magnetic shear, determines box size in x direction according to
• $L_x = L_y jtwist / (2 \pi \hat{s})$
• Also affects the number of "connections" at each ky when linked boundary conditions are selected in the dist_fn_knobs namelist.
• Internally initialised to $jtwist=MAX(Int[2\pi\hat{s}+0.5],1)$ such that $L_x \sim L_y$ except for very small shear ($\hat{s}<\sim 0.16$).
ly Float 0.0 ly
• Box size in y direction.
• If ly=0, it is set to be 2*pi*y0 (below).
n0 Integer 0 n0
• Number of toroidal mode numbers: if set, overrides y0... y0=1.0/(n0*rhostar_box*drhodpsi)
naky Integer 1 naky
• The actual number of ky modes (do not use for nonlinear runs, use ny). If left as zero (recommended), automatically set to (ny-1)/3+1.
nkpolar Integer 0 nkpolar
ntheta0 Integer lntheta0,ntheta0_private,size(akx) ntheta0
• If left as zero (recommended), automatically set to 2*((nx-1)/3)+1.
nx Integer 0 nx
• The number of kx modes: the number of kx modes actually simulated (ntheta0) is equal to 2*(nx - 1)/3 + 1, due to the need to prevent aliasing.
ny Integer ny_private,yxf_lo%ny ny
• The number of ky modes: the number of ky modes actually simulated (naky) is equal to (ny - 1)/3 + 1, due to the need to prevent aliasing.
rhostar_box Float rhostar_box
• If rhostar_box and n0 are set then y0=1.0/(n0*rhostar_box*drhodpsi)
rtwist Float 0.0 rtwist
• Experts only.
x0 Float sqrt(epts(negrid)) x0
• The length of the box in the x direction (measured in the Larmour radius of species 1) if shat is 0 (ie 1e-6)
y0 Float y0
• The length of the box in the y direction (measured in the Larmour radius of species 1). Box size in y direction is 2*pi*y0.
• Note if $y0<0$ then replaced with $-1/y0$ so effectively setting the minimum wavelength captured by the box (related to aky_min).

kt_grids_single_parameters

Name Type Def CR Name Description
akx Float 0.0 akx
• kx rho (but set theta_0 instead.)
aky Float 0.4 aky
• $k_y \rho$ for the reference species. Used only in certain modes (e.g. in single mode).
n0 Integer 0 n0
• if n0>0 use toroidal mode number to override aky and set aky=n0*drhodpsi*rhostar_single
rhostar_single Float rhostar_single
• Used in conjunction with n0: aky=n0*drhodpsi*rhostar_single (if n0 is set).
theta0 Float 0.0 theta0
• theta_0

theta_grid_parameters

Name Type Def CR Name Description
akappa Float 1.0 akappa
• The flux surface elongation (only used when geoType=0, which selects the Generalised Miller analytic geometry specification).
akappri Float 0.0 akappri
• The radial gradient flux surface elongation (only used when geoType=0, which selects the Generalised Miller analytic geometry specification).
• akappri = $d\kappa/d\rho$
alpmhd Float alpmhd
• Default = 0. Do not use unless you know what you are doing.
aSurf Float 1.0 aSurf
• Minor radius of the flux surface that receives the specified shaping (only used when geoType=1, which selects the Global MHD analytic geometry specification). See Section 2.1.2 of the Analytic Geometry Specification documentation for more details.
asym Float 0.0 asym
• No longer functional.
asympri Float 0.0 asympri
• No longer functional.
btor_slab Float 0.0 btor_slab
• In the slab limit, determines the angle between the field and the background flow (which flows in an imaginary toroidal direction). It is effectively equal to $\frac{B_t}{B}=\frac{u_{\parallel}}{u}$.
deltam Float 1.0 deltam
• The magnitude of the mMode shaping effect (only used when geoType=2 or 3, which selects the Generalised Elongation or Fourier analytic geometry specifications). See Sections 2.1.3 and 2.1.4 of the Analytic Geometry Specification documentation for more details.
deltan Float 1.0 deltan
• The magnitude of the nMode shaping effect (only used when geoType=2 or 3, which selects the Generalised Elongation or Fourier analytic geometry specifications). See Sections 2.1.3 and 2.1.4 of the Analytic Geometry Specification documentation for more details.
deltampri Float 0.0 deltampri
• Radial derivative of the magnitude of the mMode shaping effect (only used when geoType=2 or 3, which selects the Generalised Elongation or Fourier analytic geometry specifications). See Sections 2.1.3 and 2.1.4 of the Analytic Geometry Specification documentation for more details.
deltanpri Float 0.0 deltanpri
• Radial derivative of the magnitude of the nMode shaping effect (only used when geoType=2 or 3, which selects the Generalised Elongation or Fourier analytic geometry specifications). See Sections 2.1.3 and 2.1.4 of the Analytic Geometry Specification documentation for more details.
delta2 Float 1.0 delta2
• The elongation of the flux surface labeled by aSurf (only used when geoType=1, which selects the Global MHD analytic geometry specifications). See Section 2.1.2 of the Analytic Geometry Specification documentation for more details.
delta3 Float 1.0 delta3
• The triangularity of the flux surface labeled by aSurf (only used when geoType=1, which selects the Global MHD analytic geometry specifications). See Section 2.1.2 of the Analytic Geometry Specification documentation for more details.
eps Float 0.3 eps
• Controls particle trapping (among other things) in simple geometric models. $\epsilon = r/R$
epsl Float 0.3 epsl
• $\epsilon_\ell = \frac{2 L_{ref}}{ R}$ Sets curvature drift in s-alpha model, where $L_{ref}$ is the GS2 equilibrium reference normalisation length and R is the major radius at the centre of the flux surface.
geoType Integer 0 geoType
• Selects between different analytic geometry specifications (only used when iflux=0 and local_eq=T): geoType=0 selects the Generalised Miller, geoType=1 selects the Global MHD, geoType=2 selects the Generalised Elongation, and geoType=3 selects the Fourier specification. See Section 2.1 of the Analytic Geometry Specification documentation for more details.
kp Float kp
• kp sets parallel wavenumber and box length in slab geometry. $k_p = \frac{2 \pi L_{ref}}{L_z}$.
• always use kp instead of pk in slab geometry (if kp > 0 then gs2 sets pk = 2*kp)
• in slab limit $shat = \frac{L_z}{2 \pi L_s} = \frac{L_{ref}}{k_p L_s}$ : nb if kp = 1, $shat = \frac{L_{ref}}{L_s}$, where L_s is the magnetic shear scale length.
mMode Integer 2 mMode
• First flux surface shaping mode number (only used when geoType=2 or 3, which selects the Generalised Elongation or Fourier analytic geometry specifications). See Sections 2.1.3 and 2.1.4 of the Analytic Geometry Specification documentation for more details.
nMode Integer 3 nMode
• Second flux surface shaping mode number (only used when geoType=2 or 3, which selects the Generalised Elongation or Fourier analytic geometry specifications). See Sections 2.1.3 and 2.1.4 of the Analytic Geometry Specification documentation for more details.
nperiod Integer 1,2 nperiod
• Sets the number of $2\pi$ segments along equilibrium magnetic field to include in simulation domain. $N_{\rm segments} = (2n_{\rm period} - 1)$.
• Ignored in some cases
ntheta Integer 24,32,64 ntheta

Rough number of grid points along equilibrium magnetic field between $\theta=(-\pi,\pi)$.

Actual number of grid points determined as follows:

• number of points in GS2 theta grid always odd because grid must contain both bounce points of trapped particles and one grid point at $\theta=0$
• theta grid in code runs from -ntgrid:ntgrid, with ntgrid=Int(ntheta/2) for nperiod=1.
• ntheta is ignored for some numerical equilibria
pk Float 0.3 pk
• $p_k = \frac{epsl}{q} = \frac{2 L_{ref}}{ q R}$ Sets q, the magnetic safety factor, and therefore also sets the connection length, i.e. the length of the box in the parallel direction, in terms of $L_{ref}$. Used only in high aspect ratio $s-\alpha$ equilibrium model.
qinp Float 1.5 qinp
• Sets value of the safety factor when using local toroidal equilibrium model.
raxis Float 3.0 raxis
• Major radial location of the magnetic axis (only used when geoType=1, which selects the Global MHD analytic geometry specification). See Section 2.1.2 of the Analytic Geometry Specification documentation for more details.
r_geo Float 3.0 r_geo
• When $iflux = 1$: Centerpoint of LCFS (normalized to $L_{ref}$)
• When $iflux \neq 1$: Major radius of magnetic field reference point (normalized to $L_{ref}$). Specifically, the reference magnetic field is defined to be the value of the toroidal magnetic field at R=r_geo on the flux surface labeled by rhoc.
rhoc Float 0.5,0.6,0.8,1.0 rhoc
• rhoc is flux surface label (0< rhoc< 1). Its exact meaning depends on irho. Usually rho = midplane diameter/midplane diameter of LCFS

(here, "LCFS" refers to the flux surface at a radius of L_ref. If using Miller geometry with $L_{ref} \neq a$, this is *not* the physical last closed flux surface.

• When irho = 1, rhoc = sqrt(toroidal flux)/sqrt(toroidal flux of LCFS)
• When irho = 2, rhoc = midplane diameter/(midplane diameter of LCFS). recommended
• When irho = 3, rhoc = poloidal flux/(poloidal flux of LCFS)
rmaj Float 1.0,3,3.0 rmaj
• When $iflux = 1$: Position of magnetic axis (normalized to $L_{ref}$)
• When $iflux \neq 1$: Major radius of the centre of the flux surface of interest (normalized to $L_{ref}$)
shat Float 0.0,0.75 shat
• Sets value of magnetic shear in simple geometric models.
• over-ridden by s_hat_input in theta_grid_eik_knobs for most values of bishop.
shift Float 0.0,0 shift
• shift is related to minor radial derivatives of the major radial location of the flux surface centers (i.e. the Shafranov shift), but this input variable has different physical definitions in s-alpha and other analytic equilbrium models:
• In s-alpha (i.e. equilibrium_option='s-alpha'), shift$\propto$ p' is a parameter for local $J_{\phi}$ (and NOT $B_{\theta}$ which is constant): $shift = -\frac{2epsl}{pk^2}\frac{d\beta}{d\rho}=-\frac{q^2R}{L_{ref}}\frac{d\beta}{d\rho} > 0$
• In other analytic specifications (i.e. equilibrium_option='eik' and geoType=0, 2, or 3), shift is a parameter for local $B_{\theta}$ (and NOT for $J_{\phi}$): $shift = \frac{1}{L_{ref}} \frac{dR}{d\rho} < 0$
• NB in Miller shift contains the 1st radial derivative of the Shafranov shift, BUT in s-alpha shift is related to a 2nd radial derivative of the Shafranov shift.
• in s-alpha (i.e. equilibrium_option='s-alpha'), no additional parameter is required as the piece of $J_{\phi} \propto$ p' is specified by shift.
• in other analytic specifications (i.e. equilibrium_option='eik'), an additional parameter (beta_prime) is required to specify the piece of $J_{\phi} \propto$ p'
shiftVert Float 0.0 shiftVert
• Minor radial derivative of the axial location of the flux surface centers (i.e. the vertical Shafranov shift). It is only used when equilibrium_option='eik' and geoType=0, 2, or 3 (which selects the Generalised Miller, Generalised Elongation, or Fourier analytic geometry specifications). See Sections 2.1.1, 2.1.3, and 2.1.4 of the Analytic Geometry Specification documentation for more details.
thetak Float 0.0 thetak
• The tilt angle of the elongation (only used when geoType=0, which selects the Generalised Miller specification). See Section 2.1.1 of the Analytic Geometry Specification documentation for more details.
• The tilt angle of the triangularity (only used when geoType=0, which selects the Generalised Miller specification). See Section 2.1.1 of the Analytic Geometry Specification documentation for more details.
thetam Float 0.0 thetam
• The tilt angle of the mMode shaping effect (only used when geoType=2 or 3, which selects the Generalised Elongation or Fourier analytic geometry specifications). See Sections 2.1.3 and 2.1.4 of the Analytic Geometry Specification documentation for more details.
thetan Float 0.0 thetan
• The tilt angle of the nMode shaping effect (only used when geoType=2 or 3, which selects the Generalised Elongation or Fourier analytic geometry specifications). See Sections 2.1.3 and 2.1.4 of the Analytic Geometry Specification documentation for more details.
theta2 Float 0.0 theta2
• The tilt angle of the elongation of the flux surface labeled by aSurf (only used when geoType=1, which selects the Global MHD analytic geometry specification). See Section 2.1.2 of the Analytic Geometry Specification documentation for more details.
theta3 Float 0.0 theta3
• The tilt angle of the triangularity of the flux surface labeled by aSurf (only used when geoType=1, which selects the Global MHD analytic geometry specification). See Section 2.1.2 of the Analytic Geometry Specification documentation for more details.
tri Float 0.0 tri
• The flux surface triangularity (only used when geoType=0, which selects the Generalised Miller analytic geometry specification).
• triangularity is tri = arcsin[(R(max(Z))-R_major)/r_mid]
tripri Float 0.0 tripri
• The radial gradient of the flux surface triangularity (only used when geoType=0, which selects the Generalised Miller analytic geometry specification).
• tripri = $dtri/d\rho$
zaxis Float 0.0 zaxis
• Axial location of the magnetic axis (only used when geoType=1, which selects the Global MHD analytic geometry specification). See Section 2.1.2 of the Analytic Geometry Specification documentation for more details.

theta_grid_knobs

Name Type Def CR Name Description
cvdriftknob Float 1.0 cvdriftknob
• Scales the curvature drift.
equilibrium_option String default equilibrium_option
• The equilibrium_option variable controls which geometric assumptions are used in the run. Additional namelists determine the geometric parameters according to the choice made here. Allowed values are:
• 'eik' Use routines from the geometry module, controlled mainly by the subsidiary namelists theta_grid_parameters and theta_grid_eik_knob. This includes options for Miller as well as a range of different numerical equilibrium file formats.
• 'default' Same as 'eik'
• 's-alpha' Use high aspect-ratio toroidal equilbrium (which can be simplified to slab or cylinder), controlled by the subsidiary namelist theta_grid_parameters and theta_grid_salpha_knob
• 'file' Use output from rungridgen code directly. Controlled by theta_grid_file_knobs. Note: in this case, the variables nperiod and ntheta (from the theta_grid_parameters namelist) are ignored.
• 'grid.out' Same as 'file'
gb_to_cv Fortran_Bool .false. gb_to_cv
• If true then force grad-B drift to be equal to curvature drift. This is not recommended when fbpar$\neq$0.
gbdriftknob Float 1.0 gbdriftknob

theta_grid_salpha_knobs

Name Type Def CR Name Description
alpha1 Float 0.0 alpha1
• Coefficient in model when model_option='alpha1' has been selected.
alpmhdfac Float 0.0 alpmhdfac
model_option String default model_option
• Sets the particular model for the magnetic field and related drifts.
• 's-alpha' High aspect ratio toroidal equilibrium. (Note that the curvature and grad-B drifts are equal.)
• 'default' Same as 's-alpha'
• 'alpha1','rogers','b2','normal_only',const-curv',no-curvature': See output of ingen (or contents of theta_grid.f90) until this page is improved.

theta_grid_file_knobs

Name Type Def CR Name Description
gridout_file String grid.out gridout_file
• Name of file with output from rungridgen.
no_geo_info Fortran_Bool no_geo_info

theta_grid_gridgen_knobs

Name Type Def CR Name Description
alknob Float 0.0,0.1 alknob
bpknob Float 1.0e-08 bpknob
deltaw Float 0.0 deltaw
epsknob Float epsknob
extrknob Float 0.0,10.0 extrknob
tension Float 1.0 tension
thetamax Float 0.0 thetamax
widthw Float 1.0 widthw

theta_grid_eik_knobs

Name Type Def CR Name Description
alpha_input Float alpmhd_in,bp_in alpha_input
• Used only if bishop = 5. Needs to be checked.
beta_prime_input Float -1,-0.0 beta_prime_input
• The gradient of the pressure. Strictly speaking this parameter is not $\frac{\partial \beta}{\partial \rho}$ but $\beta \frac{1}{p}\frac{\partial p}{\partial \rho}$: in other words, the gradient of the magnetic field is ignored. Used only if bishop = 4 or 9.
bishop Integer 1,5,6 bishop
• Use Bishop relations to generate metric coefficients.
• 0: Use high-aspect ratio coefficients (only for debugging)
• 1: Use actual equilibrium values of shat, p' Recommended
• 2: Use numerical equilibrium + s_hat_input and p_prime_input
• 3: Use numerical equilibrium + s_hat_input and inv_Lp_input
• 4: Use numerical equilibrium + s_hat_input and beta_prime_input
• 5: Use numerical equilibrium + s_hat_input and alpha_input
• 6: Use numerical equilibrium + beta_prime_input
• 7: Use numerical equilibrium and multiply pressure gradient by dp_mult
• 8: Use numerical equilibrium + s_hat_input and multiply pressure gradient by dp_mult
• 9: Use numerical equilibrium + s_hat_input and beta_prime_input
• Otherwise: Use magnetic shear and pressure gradient as set elsewhere.
chs_eq Fortran_Bool .false.,.true. chs_eq
• Use equilbrium data from the CHEASE file ogyropsi.dat
delrho Float 0.01 delrho
• Default usually okay
dfit_eq Fortran_Bool .false. dfit_eq
• Vacuum magnetic dipole geometry
dp_mult Float 1.0 dp_mult
• Used only if bishop = 7 or 8.
efit_eq Fortran_Bool .false.,.t.,.true. efit_eq
• Use EFIT equilibrium (EFIT, codes with eqdsk format)
eqfile String dskeq.cdf,eqfile_in,ogyropsi.dat,test8_efit.dat eqfile
• Name of file with numerical equilibrium data (if required)
equal_arc Fortran_Bool .false.,.true. equal_arc
• Change field-line coordinate. Recommended value: F
gen_eq Fortran_Bool .false. gen_eq
• Use Toq-style NetCDF equilibrium (TOQ)
gs2d_eq Fortran_Bool .false. gs2d_eq
• Read Colin Roach's GS2D equilibrium file
idfit_eq Fortran_Bool .false. idfit_eq
iflux Integer 0,1 iflux
• Choose mode of operation:
• 0: Use analytic parameterization of local toroidal MHD equilibrium (Miller).
• 1: Read equilibrium data from output of MHD Grad Shafranov solver
• 2: Running inside a transport code without numerical equilibrium
invLp_input Integer invlp_input
• Used only if bishop = 3.
irho Integer 1,2 irho
• Choose definition of flux surface coordinate
• 1: rho == sqrt(toroidal flux)/sqrt(toroidal flux of LCFS)
• 2: rho == midplane diameter/LCFS diameter Recommended
• 3: rho == poloidal flux/poloidal flux of LCFS
• NB For consistency fprim, tprim, shat, uprim, g_exb etc must be computed using same radial variable, i.e. depend on choice of irho!
isym Integer 0 isym
• 0: Recommended
• 1: Force up-down symmetry.
itor Integer 1 itor
• Do not change.
local_eq String .false.,.true. local_eq
• .true. use Miller-style local equilibrium
• .false. use other numerical equilibrium
ppl_eq Fortran_Bool .false.,.true. ppl_eq
• Use Menard-style NetCDF equilibrium (JSOLVER)
rmax Float 0.0,1.0 rmax
• Never used
rmin Float 0.01,0.05 rmin
• Never used
s_hat_input Float 0.8,1 s_hat_input
• used to overrides s_hat prescribed by the numerical equilibrium, but only if bishop=2,3,4,5,8, or 9
transp_eq Fortran_Bool .false.,F transp_eq
• Use PPL NetCDF equilibrium (psipqgrz equ'm from TRANSP/TRXPL)
writelots Fortran_Bool .false.,.t. writelots
• Write a little extra about geometry to the screen.

le_grids_knobs

A concise description of the original GS2 pitch angle and energy grid choices may be found in the article entitled "Comparison of Initial Value and Eigenvalue Codes for Kinetic Toroidal Plasma Instabilities" by M. Kotschenreuther, et al., in Computer Physics Communications, Vol. 88, page 128, 1995.

Since then the energy grid has been updated to use the Candy/Waltz grid, but the pitch angle grid remains the same.

Name Type Def CR Name Description
bouncefuzz Float bouncefuzz
• Should not have to change this
• If true use generalised quadrature scheme for velocity integrals.
test Fortran_Bool .false. le_grids_test
• Write some data to the screen and stop before doing much calculation. (Debugging only)
• Velocity space res used to calculate moments of the distribution prior to calculating general quadrature scheme. Suggested value: large! (>200).
negrid Integer -10 negrid
• Total number of energy grid points
nesub Integer 8 nesub
• Only used if advanced_egrid = F; sets number of energy grid points below ecut
nesuper Integer 2 nesuper
• Only used if advanced_egrid = F; sets number of energy grid points above ecut
new_trap_int Fortran_Bool .false. new_trap_int
ngauss Integer 5 ngauss
• 2*ngauss is the number of untrapped pitch-angles moving in one direction along field line.
nmax Integer size(dv),size(h) nmax
nterp Integer nterp
trapped_particles Fortran_Bool trapped_particles
• If set to False then the $\lambda$ grid weighting (wl) is set to zero for trapped pitch angles. This means that integrals over velocity space do not include a contribution from trapped particles which is equivalent to the situation where eps<=0.0.
• Trapped particle drifts are not set to zero so "trapped" particles still enter the source term through wdfac. At least for s-alpha the drifts are the main difference (?please correct if not true?) between the eps<=0.0 and the trapped_particles = False cases as Bmag is not a function of $\theta$ in the eps<=0.0 case whilst it is in the trapped_particles = False case.
vcut Float 2.5 vcut
• No. of standard deviations from the standard Maxwellian beyond which the distribution function will be set to 0
wgt_fac Float wgt_fac

dist_fn_knobs

Two important choices are made in this namelist: (a) The boundary conditions along the field line (b) The form of the adiabatic response (if a species is being modeled as adiabatic)

Name Type Def CR Name Description
• The form of the adiabatic response (if a species is being modeled as adiabatic). Ignored if there are electrons in the species list.
• 'no-field-line-average-term' Adiabatic species has n = Phi. Appropriate for single-species ETG simulations.
• 'default' Same as 'no-field-line-average-term'
• 'iphi00=0' Same as 'no-field-line-average-term'
• 'iphi00=1' Same as 'no-field-line-average-term'
• 'field-line-average-term' Adiabatic species has n=Phi-< Phi >. Appropriate for single-species ITG simulations.
• 'iphi00=2' Same as field-line-average-term'
• 'iphi00=3' Adiabatic species has n=Phi-< Phi >_y. Incorrect implementation of field-line-average-term.
afilter Float 0.0 afilter
• For debugging only.
apfac Float 1.0 apfac
• Leave as unity. For debugging.
boundary_option String default boundary_option
• Sets the boundary condition along the field line (i.e. the boundary conditions at theta = +- pi). Possible values are:
• 'zero', 'default', 'unconnected' - Use Kotschenreuther boundary condition at endpoints of theta grid
• 'self-periodic', 'periodic', 'kperiod=1' - Each mode is periodic in theta with itself
• 'linked' - Twist and shift boundary conditions (used for kt_grids:grid_option='box')
• 'alternate-zero' - Ignored
btor_slab Float 0.0 btor_slab
• Overrides the itor_over_B internal parameter, meant only for slab runs where it sets the angle between the magnetic field and the toroidal flow.
cllc Fortran_Bool .false. cllc
• Experimental
def_parity Fortran_Bool .false. def_parity
• True only allows solutions of single parity.
even Fortran_Bool .true. dist_fn_even
• If def_parity=T, determines allowed parity.
driftknob Float 1.0 driftknob
• Leave as unity. For debugging. Multiplies the passing particle drifts (also see tpdriftknob).
esv Fortran_Bool .false. esv
• If esv=.true. and boundary_option='linked' (i.e. flux tube simulation) then at every time step we ensure the fields are exactly single valued by replacing the field at one of the repeated boundary points with the value at the other boundary (i.e. of the two array locations which should be storing the field at the same point in space we pick one and set the other equal to the one we picked). This can be important in correctly tracking the amplitude of damped modes to very small values. Also see clean_init.
g_exb Float 0.0 g_exb
• $\frac{\rho}{q} \frac{d\Omega^{\rm GS2}}{d\rho_n}$ where $\Omega^{\rm GS2}$ is toroidal angular velocity normalised to the reference frequency $v_{t}^{\rm ref}/a$

and $\rho_n$ is the normalised flux label which has value $\rho$ on the local surface.

g_exb_error_limit Float 0.0 g_exb_error_limit
• With flow shear in single mode, constrains relative error in phi^2.
g_exb_start_time Integer -1 g_exb_start_time
• Flow shear switched on at this time.
g_exb_start_timestep Integer -1 g_exb_start_timestep
• Flow shear is switched on at this time step.
g_exbfac Float 1.0 g_exbfac
• Multiplies g_exb in the perpendicular shearing term but not in the parallel drive term. Use for simulations with purely parallel flow.
gf_lo_integrate Fortran_Bool .false. gf_lo_integrate
• Performs velocity space integration using gf_lo, rather than g_lo, data decomposition. If used without field_option = 'gf_local' in fields_knobs it is likely to give poor performance.
• If field_option = 'gf_local' in fields_knobs then this needs to be present and set to .true.
gridfac Float 1.0 gridfac
• Affects boundary condition at end of theta grid. Recommended value: 1.
include_lowflow Fortran_Bool include_lowflow
• Include calculation of terms present in the low flow limit of gyrokinetics. Many new terms... will slow calculation... don't set true unless you know what you are doing. not currently implemented : lowflow terms automatically active if gs2 compiled with LOWFLOW=on
kfilter Float 0.0 kfilter
• For debugging only.
lf_decompose Fortran_Bool .false. lf_decompose
lf_default Fortran_Bool .true. lf_default
mach Float 0.0 mach
• Number multiplying the coriolis drift
mult_imp Fortran_Bool .false. mult_imp
• Allow different species to have different values of bakdif and fexpr. Not allowed for nonlinear runs.
• If true switches on new parallel boundary condition where h=0 at incoming boundary instead of g=0.
omprimfac Float 1.0 omprimfac
• Factor multiplying the parallel shearing drive term when running with non-zero g_exb
opt_init_bc Fortran_Bool .false. opt_init_bc
• If true then use an optimised init_connected_bc. This routine can become quite expensive for large problems and currently does not scale well. The optimised routine improves serial performance but does not yet help with scaling.
opt_source Fortran_Bool .false. opt_source
• If true then use an optimised linear source calculation which uses pre-calculated coefficients, calculates both sigma together and skips work associated with empty fields. Can contribute 10-25% savings for linear electrostatic collisionless simulations. For more complicated runs the savings will likely be less. If enabled memory usage will increase due to using an additional array of size 2-4 times gnew. Can potentially slow down certain runs.
poisfac Float 0.0 poisfac
• If non-zero, quasineutrality is not enforced; poisfac= (lambda_Debye/rho)**2
test String .false. test
• For debugging only. If set then run will print various grid sizes and then stop.
tpdriftknob Float -9900000000.0 tpdriftknob
• For debugging only. Multiplies the trapped particle drifts (also see driftknob).
wfb Float 1.0 wfb
• For debugging only. Sets the boundary value for the barely trapped/passing particle.
wfb_cmr Fortran_Bool .false. wfb_cmr
zero_forbid Fortran_Bool .false. zero_forbid
• If true then force gnew=0 in the forbidden region at the end of invert_rhs_1 (this is the original behaviour).
• Nothing should depend on the forbidden region so g should be 0 here and if it's not for some reason then it shouldn't impact on results. If the results of your simulation depend upon this flag then something has likely gone wrong somewhere.

fields_knobs

Name Type Def CR Name Description
do_smart_update Fortran_Bool .false. do_smart_update
• Used with field_option='local'. If .true. and x/y distributed then in advance only update local part of field in operations like "phinew=phinew+phi" etc.
dump_response Fortran_Bool .false. dump_response
• Writes files containing the field response matrix after initialisation. This currently works for field_option='implicit' or 'local'.
• Note: We write to netcdf files by default but fall back to fortran unformatted (binary) files (which are not really portable) in the absence of netcdf.
field_local_allreduce Fortran_Bool .false. field_local_allreduce
• Set to true to use an allreduce (on mp_comm) in field calculation (field_option='local' only) rather than a reduction on a sub-communicator followed by a global broadcast.
• Typically a little faster than default performance but may depend on MPI implementation.
field_local_allreduce_sub Fortran_Bool .false. field_local_allreduce_sub
• Set to true, along with field_local_allreduce and intspec_sub, to replace the allreduce used in field calculation with an allreduce on a sub-communicator followed by a reduction on a "perpendicular" communicator.
• Typically a bit faster than default and scales slightly more efficiently.
• Note if this option is active only proc0 has knowledge of the full field arrays. Other processors know the full field for any supercell (connected x-y domains) for which it has any of the xy indices local in the g_lo layout.
field_local_tuneminnrow Fortran_Bool .false. field_local_tuneminnrow
• Set to true when using field_option='local' to set the automatically tune, and select the best performing, minimum block size (in a single supercell) assigned to a single processor. This can improve performance, but is not guaranteed to.
field_option String default field_option
• The field_option variable controls which time-advance algorithm is used for the linear terms. Allowed values are:
• 'implicit' Advance linear terms with Kotschenreuther's implicit algorithm.
• 'default' Same as 'implicit'
• 'local' Same implicit algorithm as 'implicit' but with different data decomposition (typically much faster for flux tube runs).
• 'gf_local' Same as 'local' but with gf_lo field decomposition. To use this you also need to set gf_lo_integrate= .true. in dist_fn_knobs and gf_local_fields = .true. in layout_knobs
• 'explicit' Use second-order Runge-Kutta. Experimental.
• 'test' Use for debugging.
field_subgath Fortran_Bool .false. field_subgath
• Set to true to use allgatherv to fetch parts of the field update vector calculated on other procs. When false uses a sum_allreduce instead. This doesn't rely on sub-communicators so should work for any layout and processor count.
• Note: This only impacts field_option='implicit'
force_maxwell_reinit Fortran_Bool .true. force_maxwell_reinit
minnrow Integer 64 minnrow
• Used with field_option='local' to set the minimum block size (in a single supercell) assigned to a single processor. Tuning this parameter changes the balance between work parallelisation and communication. The lower this is set the more communication has to be done but the fewer processors don't get assigned work (i.e. helps reduce computation time). The optimal value is likely to depend upon the size of the problem and the number of processors being used. Furthermore it will effect intialisation and advance in different ways.
• Reads files containing the field response matrix and uses to initialise GS2s response matrix rather than using the usual initialisation process.
remove_zonal_flows_switch Fortran_Bool .false. remove_zonal_flows_switch
• Delete zonal flows at every timestep.
response_dir String "" response_dir
• Sets location in which to store/look for response dump files.
• Note We don't currently check that this location exists before attempting to use it, which could cause problems.
• The default is to save them in the working directory.

knobs

Name Type Def CR Name Description
avail_cpu_time Float 10000000000.0 avail_cpu_time
• Specify the available wall clock time in seconds. GS2 will start to exit up to 5 minutes before this time is up. This ensures that all the output files are written correctly. CodeRunner automatically sets this quantity unless it is given the value false.
delt Float delt
• Timestep, in units of $a/v_{t0}$. For linear runs, this value does not change. For nonlinear runs, the timestep used by the code will not be allowed to exceed this value.
delt_option String default delt_option
• Determines how the initial timestep is set. Options: "default", "set_by_hand" (identical to "default") and "check_restart".
• When delt_option="default", the initial timestep is set to delt.
• If delt_option="check_restart" when restarting a job, the initial timestep will be set to the last timestep of the job you are restarting, even if delt is larger. Thus, you usually want to set delt_option="check_restart" when restarting a job and delt_option="default" otherwise.
do_eigsolve Fortran_Bool .false. do_eigsolve
• If true then use eigensolver instead of initial value solver. Only valid for executables compiled with WITH_EIG=on and linked with PETSC+SLEPC libraries. Should only be used in linear simulations with a single ky and theta0.
eqzip Fortran_Bool .false. eqzip
• Default = .false. Do not evolve certain $k$ modes in time. Set this to true only if you know what you are doing. True only for secondary/tertiary instability calculations.
eqzip_option String none eqzip_option
fapar Float 0.0,1.0 fapar
• Multiplies $A_\parallel$ throughout. Set to zero for electrostatic calculations, or unity for electromagnetic. Set to zero if $\beta = 0$.
faperp Float 0.0 faperp
• Multiplies A_perp. Use 1 for high beta, 0 otherwise. Deprecated: use fbpar instead. Defaults to zero. Do not change this value unless you know what you are doing.
fbpar Float -1.0,0.0 fbpar
• Multiplies $B_\parallel$ throughout. Set to zero or unity, depending on whether you want to include physics related to $\delta B_\parallel$. Set to zero if $\beta = 0$.
fixpar_secondary Integer fixpar_secondary
fphi Float fphi
• Multiplies $\Phi$ (electrostatic potential) throughout. Useful for debugging. Non-experts use 1.0
harris Fortran_Bool .false. harris
• Default = .false. Do not set to true unless you know what you are doing.
immediate_reset Fortran_Bool .true. immediate_reset

Determines the behaviour when the CFL condition is broken in the nonlinear term:

• .true.: abort the current timestep and adjust delt
• .false.: finish the current timestep, then adjust delt
margin Float 0.05 margin
• Obsolete. Fraction of T3E batch job used for finishing up.
margin_cpu_time Float 300.0 margin_cpu_time
• Time (in seconds) before avail_cpu_time at which finalisation triggered. May need to set this quite large for large problems to make certain the run finishes cleanly.
neo_test Fortran_Bool .false. neo_test
• If true, GS2 exits after writing out neoclassical quantities of interest.
nstep Integer nstep
• Number of timesteps that will be taken, unless the code stops for some (usually user-specified) reason.
secondary Fortran_Bool .false.,.true. secondary
• Default = .false. Do not set to true unless you know what you are doing.
tertiary Fortran_Bool .false. tertiary
• Default = .false. Do not set to true unless you know what you are doing.
trinity_linear_fluxes Fortran_Bool .false. trinity_linear_fluxes
• If true and running linearly, return linear diffusive flux estimates to Trinity.
wstar_units String .false. wstar_units
• Default = .false. Make the timestep proportional to $k_y \rho$. This can be useful for linear stability calculations that have a wide range of $k_y$ values. Do not set to true for nonlinear runs. Be aware that the units of some output quantities can change when wstar_units = .true.

reinit_knobs

Name Type Def CR Name Description
abort_rapid_time_step_change Fortran_Bool .true. abort_rapid_time_step_change
• If true (default), exit if time step changes rapidly, that is, if the time step changes at four consecutive time steps.
• When the time step needs to be changed it is adjusted by this factor (i.e dt-->dt/delt_adj or dt-->dt*delt_adj when reducing/increasing the timestep).
• For implicit non-linear runs good choice of delt_adj can make a moderate difference to efficiency. Need to balance time taken to reinitialise against frequency of time step adjustments (i.e. if your run takes a long time to initialise you probably want to set delt_adj to be reasonably large).
delt_cushion Float 1.5 delt_cushion
• Used in deciding when to increase the time step to help prevent oscillations in time step around some value. We only increase the time step when it is less than the scaled cfl estimate divided by delt_adj*delt_cushion (whilst we decrease it as soon as the time step is larger than the scaled cfl estimate).
delt_minimum Float 1.0e-05 delt_minimum
• The minimum time step allowed is delt_minimum. If the code wants to drop below this value then the run will end.
in_memory Fortran_Bool .false. in_memory
• If true then attempts to create temporary copies of the dist fn and fields in memory to be restored after the time step reset rather than dumping to fields.
• This could be faster on machines with slow file systems.
• If the required memory allocation fails then we set in_memory=.false. and fall back to the traditional file based approach.

layouts_knobs

Name Type Def CR Name Description
fft_measure_plan Fortran_Bool .true. fft_measure_plan
• When set to true fft will use timing data during plan creation to select optimal settings. When false it will fall back to a simple heuristic estimate.
fft_use_wisdom Fortran_Bool fft_use_wisdom
fft_wisdom_file String fft_wisdom_file
gf_local_fields Fortran_Bool .false. gf_local_fields
• Enable the creation and setup of gf_lo data decomposition. This is required if using field_option = 'gf_local' in fields_knobs.
intmom_sub Fortran_Bool .false. intmom_sub
• When set to true we will use sub-communicators to do the reduction associated with calculating moments of the dist. fn. These sub-communicators involve all procs with a given XYS block.
• This is particularly advantageous for collisional runs which don't use LE layouts.
• PLEASE NOTE: These changes only effect calls to integrate_moments with complex variables and where the optional 'all' parameter is supplied. There is no gather of data from other procs so the integration result is only known for the local XYS block. This could cause a problem for diagnostics which want to write the full array if they also pass "all" (see [1])
intspec_sub Fortran_Bool .false. intspec_sub
• When set to true we will use sub-communicators to do the reduction associated with calculating species integrated moments of the dist. fn. These sub-communicators involve all procs with a given XY block.
• This should help improve the field update scaling.
• PLEASE NOTE: Unlike intmom_sub we currently gather the results from other procs such that we are sure to have the whole array populated correctly.
layout String llayout,lxyes layout
• Determines the way the grids are laid out in memory. Rightmost is parallelised first.
• Can be 'yxles', 'lxyes', 'lyxes', 'lexys','xyles'
• Strongly affects performance on parallel computers
• In general avoid parallelizing over x. For this reason 'lxyes' is often a good choice.
• Depending on the type of run you are doing, and how many processors you are using, the optimal layout will vary.
• In nonlinear runs FFTs are taken in x and y, so keeping these as local as possible (i.e. keeping xy to the left in layout) will help these.
• In calculating collisions we need to take derivatives in l and e, hence keeping these as local as possible will help these.
• The best choice will vary depending on grid sizes generally for linear runs with collisions 'lexys' is a good choice whilst for nonlinear runs (with or without collisions) 'xyles' (or similar) is usually fastest.
local_field_solve String .false. local_field_solve
• Strongly affects initialization time on some parallel computers.
• Recommendation: Use T on computers with slow communication networks.
• It's probably worth trying changing this on your favourite machine to see how much difference it makes for you.
max_unbalanced_xxf Float 0.0,1.0 max_unbalanced_xxf
max_unbalanced_yxf Float 0.0,1.0 max_unbalanced_yxf
opt_local_copy Fortran_Bool .false. opt_local_copy
• Setting to .true. enables optimising redistribute code, used in FFTs for evaluating nonlinear terms, that avoids indirect addressing.

This can introduces worthwhile savings in nonlinear GS2 simulations at lower core counts.

opt_redist_init Fortran_Bool .false. opt_redist_init
• Set to true to use optimised initialisation routines for creating redist objects. This should be beneficial for all but the smallest number of processors.
opt_redist_nbk Fortran_Bool .false. opt_redist_nbk
• Set to true to use non-blocking comms in the redistribute routines.
opt_redist_persist Fortran_Bool .false. opt_redist_persist
• Set to true to use persistent (non-blocking) comms in the redistribute routines.
• Must also set opt_redist_nbk=.true.
• Can help improve scaling efficiency at large core counts, but can cause slow down at low core counts.
opt_redist_persist_overlap Fortran_Bool .false. opt_redist_persist_overlap
• Set to true to try to overlap the mpi and local parts of the gather/scatter routines.
• Should only be used with opt_redist_persist=.true.
• See Optimising your runs for more details.
unbalanced_xxf Fortran_Bool .false. unbalanced_xxf
• Setting to .true. allows GS2 to adopt a more flexible domain decomposition of the xxf data type (used in nonlinear FFTs).
• By default GS2 allocates each MPI task with the same uniform blocksize in xxf_lo, one task may have a smaller block of data, and other tasks may be empty. There is no attempt to keep both x and y as local as possible, and sometimes large MPI data transfers are required to map from xxf to yxf and vice-versa during FFTs.
• With "unbalanced_xxf = .true.", two slightly different blocksizes are chosen in order to keep both x and y as local as possible, and avoid this potentially large MPI communication overhead. The level of imbalance is limited by max_unbalanced_xxf.
• See Adrian Jackson's DCSE report "Improved Data Distribution Routines for Gyrokinetic Plasma Simulations"
unbalanced_yxf Fortran_Bool .false. unbalanced_yxf
• Setting to .true. allows GS2 to adopt a more flexible domain decomposition of the yxf data type (used in nonlinear FFTs).
• By default GS2 allocates each MPI task with the same uniform blocksize in yxf_lo, one task may have a smaller block of data, and other tasks may be empty. There is no attempt to keep both x and y as local as possible, and sometimes large MPI data transfers are required to map from xxf to yxf and vice-versa during FFTs.
• With "unbalanced_yxf = .true.", two slightly different blocksizes are chosen in order to keep both x and y as local as possible, and avoid this potentially large MPI communication overhead. The level of imbalance is limited by max_unbalanced_yxf.
• See Adrian Jackson's DCSE report "Improved Data Distribution Routines for Gyrokinetic Plasma Simulations"

collisions_knobs

Name Type Def CR Name Description
• If adjust is .true., transform from the gyro-averaged dist. fn., g, to the non-Boltzmann part of delta f, h, when applying the collision operator
cfac Float 0.0,1.0 cfac
• Factor multiplying FLR terms in collision operator. 1.0 by default. Set to 0.0 to turn off FLR corrections.
collision_model String default collision_model
• Collision model used in the simulation.
• default = pitch angle scattering and energy diffusion
• collisionless,none = collisionless
• lorentz = pitch angle scattering only
• ediffuse = energy diffusion only
• krook = use home made krook operator (no reason to use this!)
conservative Fortran_Bool .true. conservative
• Set to .true. to guarantee exact conservation properties.
conserve_moments Fortran_Bool .true. conserve_moments
• Set to .true. to guarantee collision operator conserves momentum and energy.
const_v Fortran_Bool .false. const_v
ediff_scheme String default ediff_scheme
ei_coll_only Fortran_Bool .false. ei_coll_only
etol Float 0.02 etol
etola Float 0.02 etola
ewindow Float 0.01 ewindow
ewindowa Float 0.01 ewindowa
heating Fortran_Bool .false. heating
• Set to .true. to compute collisional heating.
hypermult Fortran_Bool .false. hypermult
lorentz_scheme String default lorentz_scheme
ncheck Integer 10,100 ncheck
resistivity Fortran_Bool .true. resistivity
special_wfb_lorentz Fortran_Bool .true. special_wfb_lorentz
• If true (the default) then the wfb is treated in a special way in the lorentz collision operator. This is the standard behaviour. Setting to false has been seen to help an issue in linear flux tube simulations in which the zonal modes at large kx grow rapidly.
split_collisions Fortran_Bool .false. split_collisions
• If true, then collisions are removed from the Kotschenreuther algorithm and evolved separately. This has the same formal accuracy as including the collisions in the Kotschenreuther advance, but requires fewer calls to the collisions module, and therefore fewer memory redistributes. This gives a speed up of between ~20% and ~60%, depending on processor count.
• If false, the old method is used. This is the default, to prevent discrepancies with old results.
test Fortran_Bool .false. test_collisions
use_le_layout Fortran_Bool .true. use_le_layout
• Use more efficient layouts for le grid
vary_vnew Fortran_Bool .false. vary_vnew
vnfac Float 1.1 vnfac
vnslow Float 0.9 vnslow

hyper_knobs

Name Type Def CR Name Description
const_amp String .false. const_amp
• Determines whether hyperviscosity includes time dependent amplitude factor when calculating damping rate. Recommend TRUE for linear runs and FALSE for nolinear runs, since amplutide of turbulence grows linearly with time in linear run.
d_hyper Float d_hyper
d_hyperres Float d_hyperres
d_hypervisc Float d_hypervisc
• Sets hyperviscosity parameter multiplying damping term. See Belli (2006) thesis for more information.
damp_zonal_only Fortran_Bool .false. damp_zonal_only
gridnorm Fortran_Bool .true. gridnorm
hyper_option String default hyper_option
• Should be set to 'default','none','visc_only', 'res_only', or 'both'. 'default' and 'none' are identical.
include_kpar Fortran_Bool .false. include_kpar
isotropic_shear String .true. isotropic_shear
nexp Integer 2 nexp
omega_osc Float 0.4 omega_osc

nonlinear_terms_knobs

Name Type Def CR Name Description
C_par Float c_par
• Ignored.
C_perp Float c_perp
• Ignored.
cfl Float 0.1 cfl
• The maximum delt < cfl * min(Delta_perp/v_perp)
flow_mode String default flow_mode
• Experimental
nl_forbid_force_zero Fortran_Bool nl_forbid_force_zero
nonlinear_mode String default nonlinear_mode
• Should the nonlinear terms be calculated?
• 'none', 'default', 'off': Do not include nonlinear terms, i.e. run a linear calculation.
• 'on' Include nonlinear terms.
p_x Float 6.0 p_x
• Ignored.
p_y Float 6.0 p_y
• Ignored.
p_z Float 6.0 p_z
• Ignored.
zip Fortran_Bool zip
• Experts only (for secondary/tertiary calculations).

Name Type Def CR Name Description

species_knobs

Name Type Def CR Name Description
nspec Integer 2 nspec
• Number of kinetic species evolved.

species_parameters

There should be a separate namelist for each species. For example, if there are two species, there will be namelists called species_parameters_1 and species_parameters_2. Charge, mass, density and temperature for each species are relative to some reference species.

Name Type Def CR Name Description
bess_fac Float 1.0 bess_fac
• Multiplies the argument of the Bessel function for this species. Useful for removing the effect of the Bessel functions (set to 0.0)
dens Float 1.0 dens
• Density
dens0 Float 1.0 dens0
fprim Float 2.2 fprim
• Normalised inverse density gradient: $-1/n (dn/d\rho)$ (Note here $\rho$ is the normalised radius $\rho/L_{ref}$)
gamma_ae Float gamma_ae
• Alpha electron collion rate. Normalisation chosen so that this parameter should be roughly the same as nu_ee.
gamma_ai Float gamma_ai
• Alpha ion collion rate. Normalisation chosen so that this parameter should be roughly the same as nu_ii.
mass Float 1.0 mass
• Mass
nu Float -1.0 nu
nu_h Float 0.0 nu_h
nustar Float -1.0 nustar
source Float 0.0 source
• Sets the normalised source for alphas. If set negative will be automatically adjusted to give the specified alpha density.
sprim Float sprim
temp Float 1.0 temp
• Temperature
tpar0 Float 0.0 tpar0
tperp0 Float 0.0 tperp0
tprim Float 6.9 tprim
• Normalised inverse temperature gradient: $-1/T (dT/d\rho)$ (Note here $\rho$ is the normalised radius $\rho/L_{ref}$)
type String default type
• Type of species:
• 'ion' Thermal ion species
• 'default' Same as 'ion'
• 'electron' Thermal electron species
• 'e' Same as 'electron'
• 'beam' Slowing down distribution (Requires advanced_egrid = F)
• 'slowing_down' Same as 'beam'
• 'fast' Same as 'beam'
• 'alpha' Same as 'beam'
u0 Float 1.0 u0
uprim Float 0.0 uprim
•  ?
uprim2 Float 0.0 uprim2
vnewk Float 0.0 vnewk
• Collisionality parameter: For species $s$, vnewk = $\nu_{ss} L_{ref} / v_{ref}$ where $L_{ref}$ is the reference length (half-minor-radius at the elevation of the magnetic axis), $v_{ref} = \sqrt{2 T_{ref} / m_{ref}}$ is the reference thermal speed (not the thermal speed of species $s$!), $\nu_{ss} = \frac{\sqrt{2} \pi n_s Z_s^4 e^4 \ln(\Lambda)}{\sqrt{m_s} T_s^{3/2}}$ is a dimensional collision frequency, $e$ is the proton charge, $\ln(\Lambda)$ is the Coloumb logarithm, and ($Z_s, T_s, n_s, m_s$) are the (charge, temperature, density, mass) of species $s$. (The dimensional collision frequency given here is in Gaussian units. For SI units, include an extra factor $(4 \pi \epsilon_0)^2$ in the denominator of the definition of $\nu_{ss}$.)
z Float 1 z
• Charge

dist_fn_species_knobs

Name Type Def CR Name Description
bakdif Float bakdif_out bakdif
• Spatial implicitness parameter. Any value greater than 0 adds numerical dissipation (usually necessary). bakdif=0 is 2cd-order space-centered, bakdif=1.0 is fully upwinded.
• Recommended value for electrostatic runs: 0.05. For electromagnetic runs, bakdif should be 0.
bd_exp Integer bd_exp_out bd_exp
fexpi Float aimag(fexp_out) fexpi
fexpr Float real(fexp_out) fexpr
• Temporal implicitness parameter. Any value smaller than 0.5 adds numerical dissipation. fexpr=0.5 is 2cd order time-centered, fexpr=0 is fully implicit backward Euler, fexpr=1.0 is fully explicit forward Euler.
• Recommended value: 0.48

init_g_knobs

Name Type Def CR Name Description
a0 Float 0.0 a0
apar0 Float 0.0 apar0
aparamp Complex aparamp
• Used in initialization for the Orszag-Tang 2D vortex problem
b0 Float 0.0 b0
chop_side Fortran_Bool .true. chop_side
• Rarely needed. Forces asymmetry into initial condition. Warning: This does not behave as one may expect in flux tube simulations (see clean_init), this can be important as the default is to use chop_side.
clean_init Fortran_Bool .false. clean_init
• Used with ginit_option='noise'. Ensures that in flux tube simulations the connected boundary points are initialised to the same value. Also allows for chop_side to behave correctly in flux tube simulations.
den0 Float 1.0 den0
• Parameters for setting up special initial conditions.
den1 Float 0.0 den1
• Parameters for setting up special initial conditions.
den2 Float 0.0 den2
• Parameters for setting up special initial conditions.
dphiinit Float 1.0 dphiinit
eq_mode_n Integer 0 eq_mode_n
eq_mode_u Integer 1 eq_mode_u
eq_type String sinusoidal eq_type
even Fortran_Bool .true. even
• Sometimes initial conditions have definite parity; this picks the parity in those cases.
force_single_kpar Fortran_Bool force_single_kpar
• When initialised with single parallel mode, sets other modes to zero at every time step.
ginit_option String default ginit_option
• Sets the way that the distribution function is initialized. There are many possible choices.
• 'default' This gives a gaussian in theta (see width0)
• 'noise' This is the recommended selection (but not the default). Pretty random.
• 'test1'
• 'xi'
• 'xi2'
• 'zero'
• 'test3'
• 'convect'
• 'rh'
• 'many' This is the option to read the (many) restart files written by a previous run. Use for restarts
• 'small'
• 'file'
• 'cont'
• 'kz0' initialise only with k_parallel=0
• 'nl'
• 'nl2'
• 'nl3'
• 'nl4'
• 'nl5'
• 'nl6'
• 'gs'
• 'kpar'
• 'zonal_only' Restart but set all non-zonal components of the potential and the distribution function to 0. Noise can be added to these other components by setting iphiinit > 0.
• 'single_parallel_mode' Initialise only with a single parallel mode specified by either ikpar_init for periodic boundary conditions or kpar_init for linked boundary conditions. Intended for linear calculations.
• 'all_modes_equal' Initialise with every single parallel and perpendicular mode given the same amplitude. Intended for linear calculations.
• 'eig_restart' Uses the restart files written by the eigensolver. Also see restart_eig_id.
• 'stationary_mode' Initialises the distribution function such that it is a time-independent solution to the gyrokinetic equation when collisions are neglected and only one mode (with aky = 0) is present. See Section 4 of the Analytic Geometry Specification documentation for more details.
ikk Integer ikk
• Used only for secondary/tertiary calculations.
ikkk Integer ikkk
ikpar_init Integer 0 ikpar_init
ikx_init Integer -1 ikx_init
• Only initialise a single kx with noise. This input parameter is used when noise is being initialised. If specified, i.e. if it is set greater than zero, noise will only be initialised for itheta0 = ikx_index, i.e. for the mode indexed by ikx_index. this is useful for linear runs with flow shear, to track the evolution of a single Lagrangian mode.
imfac Float 0.0 imfac
• Used in rare cases.
input_check_recon Fortran_Bool .false. input_check_recon
itt Integer itt
• Used only for secondary/tertiary calculations.
ittt Integer ittt
kpar_init Float 0.0 kpar_init
left Fortran_Bool .true. left
• Chop out left side in theta.
new_field_init Fortran_Bool .true. new_field_init
nkxy_pt Complex cmplx(0.,0.) nkxy_pt
null_apar Fortran_Bool .false. null_apar
null_bpar Fortran_Bool .false. null_bpar
null_phi Fortran_Bool .false. null_phi
phiamp Complex phiamp
• Used in initialization for the Orszag-Tang 2D vortex problem.
phifrac Float 0.1 phifrac
phiinit Float 1.0 phiinit
• Average amplitude of initial perturbation of each Fourier mode.
phiinit0 Float 0.0 phiinit0
phiinit_rand Float 0.0 phiinit_rand
• Amplitude of random perturbation for ginit_recon3 (R Numata)
prof_width Float -0.1 prof_width
• Only applies if GS2 has been build with USE_PARALLEL_NETCDF=on. If .true., restart the old way from many restart files, if .false. use the new single restart file.
refac Float 1.0 refac
• Used in rare cases.
restart_dir String ./,trim(restart_dir)//"/" restart_dir
• Directory in which to write/read restart files. Make sure this exists before running.
restart_eig_id Integer restart_eig_id
• Used to select with eigensolver generated restart file to load. Sets <id> in restart_file//eig_<id>//.<proc> string used to set filename. Note this is zero indexed.
restart_file String file,trim(restart_dir)//trim(restart_file),trim(restart_file(1:ind_slash))//trim(restart_dir)//trim(restart_file(ind_slash+1:)),trim(run_name)//".nc" restart_file
• Base of filenames with restart data.
scale Float 1.0 scale
• Allows rescaling of amplitudes for restarts.
tpar0 Float 0.0 tpar0
• Parameters for setting up special initial conditions.
tpar1 Float 0.0 tpar1
• Parameters for setting up special initial conditions.
tpar2 Float 0.0 tpar2
• Parameters for setting up special initial conditions.
tperp0 Float 0.0 tperp0
• Parameters for setting up special initial conditions.
tperp1 Float 0.0 tperp1
• Parameters for setting up special initial conditions.
tperp2 Float 0.0 tperp2
• Parameters for setting up special initial conditions.
tstart Float -1.0,0.0 tstart
• Force t=tstart at beginning of run.
ukxy_pt Complex cmplx(0.,0.) ukxy_pt
upar0 Float 0.0 upar0
• Parameters for setting up special initial conditions.
upar1 Float 0.0 upar1
• Parameters for setting up special initial conditions.
upar2 Float 0.0 upar2
• Parameters for setting up special initial conditions.
width0 Float -3.5 width0
• Initial perturbation has Gaussian envelope in theta, with width width0
zf_init Float 1.0 zf_init
• Amplitude of initial zonal flow perturbations relative to other modes

gs2_diagnostics_knobs

Controls what information is output by GS2 during and at the end of a simulation.

Name Type Def CR Name Description
conv_max_step Integer 80000 conv_max_step
conv_min_step Integer 4000 conv_min_step
conv_nstep_av Integer 4000 conv_nstep_av
conv_nsteps_converged Integer 10000 conv_nsteps_converged
conv_test_multiplier Float conv_test_multiplier
dump_check1 Fortran_Bool .false. dump_check1
• Field-line avg of Phi written to dump.check1
dump_check2 Fortran_Bool .false. dump_check2
• Apar(kx, ky, igomega) written to dump.check2
dump_fields_periodically Fortran_Bool .false. dump_fields_periodically
• Phi, Apar, Bpar written to dump.fields.t=(time). This is expensive!
exit_when_converged Fortran_Bool .true. exit_when_converged
• When the frequencies for each k have converged, the run will stop.
file_safety_check Fortran_Bool .true. file_safety_check
• If .true. and either save_for_restart or save_distfn are true then checks that files can be created in restart_dir near the start of the simulation. This should probably be turned on by default after some "in the wild" testing.
igomega Integer 0 igomega
• Theta index at which frequencies are calculated.
make_movie Fortran_Bool .false. make_movie
navg Integer 10,100 navg
• Any time averages performed over navg timesteps.
nmovie Integer 1000 nmovie
nsave Integer -1 nsave
• Write restart files every nsave timesteps
nwrite Integer 10,100 nwrite
• Output diagnostic data every nwrite timesteps.
nwrite_mult Integer 10 nwrite_mult
• Multiplies nwrite to determine when large/expensive to calculate datasets such as the parallel correlation function are written to file.
ob_midplane Fortran_Bool ob_midplane
• If write_moments is true, then:
• if ob_midplane is true, then write the various velocity moments of the distribution function as functions of t ONLY at THETA=0 (and set write_full_moments_notgc = false),
• if ob_midplane is false, then write moments as functions of t at ALL THETA.
omegatinst Float 1.0,1000000.0 omegatinst
• If any growth rate is greater than omegatinst, assume there is a numerical instability and abort.
omegatol Float -0.001 omegatol
• In linear runs GS2 will exit if the growth rate has converged to an accuracy of one part in 1/omegatol. Set negative to switch off this feature.
print_flux_line Fortran_Bool .false. print_flux_line
• Instantaneous fluxes output to screen every nwrite timesteps
print_line Fortran_Bool .false.,.true. print_line
• Estimated frequencies and output to the screen/stdout every nwrite timesteps
save_distfn Fortran_Bool .false. save_distfn
• If true, saves the restart files with name 'rootname.nc.dfn.<proc>' with lots of extra detail about the dist function --- velocity space grids and so on, when GS2 exits.
save_for_restart Fortran_Bool .false.,.true. save_for_restart
• If true then restart files written to the local folder and the simulation can be restarted from the point it ended.
• Restart files written to restart_file.PE#.
• Recommended for nonlinear runs.
save_many Fortran_Bool .false. save_many
• Only applies if GS2 has been build with USE_PARALLEL_NETCDF=on. If .true., save for restart the old way to many restart files, if .false. save the new single restart file.
use_nonlin_convergence Fortran_Bool .false. use_nonlin_convergence
write_apar_over_time Fortran_Bool .false. write_apar_over_time
• If this variable is set to true then the entire field A_parallel will be written to the NetCDF file every nwrite. This can cause the NetCDF file to be huge, if resolution is large or nwrite is small.
write_ascii Fortran_Bool .true. write_ascii
• If true, some data is written to runname.out
• Also controls the creation of a large number of ascii data files (such as <run_name>.fields). Many of the write_* settings in this namelist will only have an effect when write_ascii= .TRUE.
write_avg_moments Fortran_Bool .false. write_avg_moments
• Ignored unless grid_option='box'
• Flux surface averaged low-order moments of g written to runname.out.nc
• If (write_ascii = T) flux surface averaged low-order moments of g written to runname.moments
write_bpar_over_time Fortran_Bool .false. write_bpar_over_time
• If this variable is set to true then the entire field B_parallel will be written to the NetCDF file every nwrite. Useful for making films. This can cause the NetCDF file to be huge, if resolution is large or nwrite is small.
write_cerr Fortran_Bool .false. write_cerr
write_correlation Fortran_Bool .false.,.true. write_correlation
• Write correlation function diagnostic... shows parallel correlation as a function of ky. See arXiv 1104.4514.
write_correlation_extend Fortran_Bool .false. write_correlation_extend
• If used in conjunction with write_correlation, extends the length of $\Delta \theta$ for which the correlation function is calculated.
write_cross_phase Fortran_Bool .false. write_cross_phase
write_eigenfunc Fortran_Bool .false. write_eigenfunc
• If (write_ascii = T) Normalized Phi(theta) written to runname.eigenfunc
• Write to runname.out.nc even if (write_ascii = F)
write_fields Fortran_Bool .false.,.true. write_fields
• Updates the phi, apar and bpar arrays in the netcdf output every nwrite steps. This is useful to allow the impatient to get an idea of the eigenfunction quality before the simulation ends without having to store the fields as a function of time.
• note : previously this flag triggered attempts to write phi, apar and bpar as a function of time. This behaviour is now available through the write_phi_over_time flags (and related for other fields).
write_final_antot Fortran_Bool .false. write_final_antot
• If (write_ascii = T) Sources for Maxwell eqns. written to runname.antot
• Write to runname.out.nc even if (write_ascii = F)
write_final_db Fortran_Bool .false. write_final_db
• Write final delta B.
write_final_epar Fortran_Bool .false. write_final_epar
• If (write_ascii = T) E_parallel(theta) written to runname.eigenfunc
• Write to runname.out.nc even if (write_ascii = F)
write_final_fields Fortran_Bool .false. write_final_fields
• If (write_ascii = T) Phi(theta) written to runname.fields
• Write to runname.out.nc even if (write_ascii = F)
write_final_moments Fortran_Bool .false. write_final_moments
• If (write_ascii = T) low-order moments of g written to runname.moments and int dl/B averages of low-order moments of g written to runname.amoments
• Write to runname.out.nc even if (write_ascii = F)
write_flux_line Fortran_Bool .true. write_flux_line
• If (write_ascii = T) instantaneous fluxes output to runname.out every nwrite timesteps
write_full_moments_notgc Fortran_Bool .false. write_full_moments_notgc
write_g Fortran_Bool .false. write_g
• Write the distribution function to the '.dist' (NetCDF?)
write_gg Fortran_Bool .false. write_gg
write_gs Fortran_Bool .false. write_gs
write_gyx Fortran_Bool .false. write_gyx
• Write dist fn at a given physical spacial point to a file
write_hrate Fortran_Bool .false. write_hrate
• Write heating rate, collisonal entropy generation etc to '.heat'
write_kpar Fortran_Bool .false. write_kpar
• Spectrum in k_parallel calculated and written.
write_line Fortran_Bool .true. write_line
• If (write_ascii = T) write estimated frequencies and growth rates to the output file (usually runname.out) every nwrite steps.
write_lorentzian Fortran_Bool .false. write_lorentzian
• Frequency Sweep Data
write_lpoly Fortran_Bool .false. write_lpoly
write_max_verr Fortran_Bool .false. write_max_verr
write_moments Fortran_Bool .false.,.true. write_moments
• If true then we write the various velocity moments of the distribution function to the netcdf file every nwrite steps.
write_nl_flux Fortran_Bool .false. write_nl_flux
• Phi**2(kx,ky) written to runname.out
write_nl_flux_dist Fortran_Bool .false. write_nl_flux_dist
• Writes the poloidally-dependent electrostatic turbulent fluxes of particles, parallel momentum, perpendicular momentum, and energy (i.e. the usual turbulent fluxes without the flux surface average) to the es_part_flux_dist, es_mom_flux_par_dist, es_mom_flux_perp_dist, and es_heat_flux_dist variables of the netCDF output file respectively. See Section 3 of the Analytic Geometry Specification documentation for more details.
write_omavg Fortran_Bool .false. write_omavg
• If (write_ascii = T) time-averaged frequencies written to runname.out every nwrite timesteps.
• Average is over navg steps.
• Worth noting that setting this to true does not result in omegaavg being written to netcdf file (see write_omega).
write_omega Fortran_Bool .false.,.true. write_omega
• If (write_ascii = T) instantaneous omega to output file every nwrite timesteps. Very heavy output.
• If true writes omega to netcdf file every nwrite timesteps.
• Also writes out omegaavg (omega averaged over navg steps) to netcdf file no matter what the value of write_omavg is.
write_parity Fortran_Bool .false. write_parity
• Writes parities in dist fn and particle fluxes
write_pflux_sym Fortran_Bool .false. write_pflux_sym
write_pflux_tormom Fortran_Bool .false. write_pflux_tormom
write_phi_over_time Fortran_Bool .false. write_phi_over_time
• If this variable is set to true then the entire field Phi will be written to the NetCDF file every nwrite. Useful for making films. This can cause the NetCDF file to be huge, if resolution is large or nwrite is small.
write_symmetry Fortran_Bool .false. write_symmetry
• Switch on a diagnostic to test the symmetry properties of the GK eqn. It calculates the momentum flux as a function of vpar, theta, and time.
write_verr Fortran_Bool .false.,.true. write_verr
• Write velocity space diagnostics to '.lpc' and '.verr' files

testgridgen

Name Type Def CR Name Description
alknob Float 0.0,0.1 alknob
auto_width Fortran_Bool .false. auto_width
bpknob Float 1.0e-08 bpknob
cv_fraction Float 0.6 cv_fraction
deltaw Float 0.0 deltaw
delth_max Float 0.5 delth_max
epsknob Float epsknob
extrknob Float 0.0,10.0 extrknob
gingrid String gingrid gingrid
gsource String eik6.out gsource
iperiod Integer 1 iperiod
max_autoiter Integer 3 max_autoiter
nfinegrid Integer 200 nfinegrid
nlambdaout Integer 20 nlambdaout
nperiodout Integer 2 nperiodout
nthetaout Integer 32 nthetaout
screenout Fortran_Bool .false. screenout
smoothknob Float 0.0 smoothknob
source Float 0.0 source
tension Float 1.0 tension
thetamax Float 0.0 thetamax
three_dim Fortran_Bool .false. three_dim
widthw Float 1.0 widthw

driver

Name Type Def CR Name Description
amplitude Float 0.0 amplitude
• Amplitude of Langevin antenna.
ant_off Fortran_Bool .false. ant_off
• Overrides all and turns off antenna if true.
t0 Float -1.0,100.0 driver_t0
nk_stir Integer 1 nk_stir
• Number of independent Fourier modes driven by antenna.
restarting Fortran_Bool restarting
w_antenna Complex 1.0+0.0i w_antenna
• Frequency of Langevin antenna.
w_dot Float 0.0 w_dot
write_antenna Fortran_Bool write_antenna
• Write antenna amplitudes to ASCII file for debugging.

stir

Name Type Def CR Name Description
a Float -1.0,0.0 stir_a
• Initial amplitude of right-moving component. It is not necessary to set a and b unless you are

doing restarts, which are rather clunky at the moment with the antenna included.

b Float -1.0,0.0 stir_b
• Initial amplitude of left-moving component. It is not necessary to set a and b unless you are

doing restarts, which are rather clunky at the moment with the antenna included.

kx Integer 1 stir_kx
• Mode number for stirring
ky Integer 1 stir_ky
• Mode number for stirring
kz Integer 1 stir_kz
• Mode number for stirring
travel Fortran_Bool .true. stir_travel
• Launches traveling wave (or standing wave if F).

source_knobs

Name Type Def CR Name Description
gamma0 Float 0.0 gamma0
• Growth rate of non-standard source (if selected above).
omega0 Float 0.0 omega0
• Frequency of non-standard source (if selected above).
phi_ext Float 0.0 phi_ext
• Amplitude of external Phi added as source term.
source0 Float 1.0 source0
• Amplitude of non-standard source (if selected above).
source_option String default source_option
• 'source_option_full' Solve GK equation in standard form (with no artificial sources)
• 'default' Same as 'source_option_full'
• 'zero' The GK distribution function will be advanced non-self-consistently.
• 'sine' The GK distribution function will be advanced non-self-consistently.
• 'cosine'The GK distribution function will be advanced non-self-consistently.
• 'test1' The GK distribution function will be advanced non-self-consistently.
• 'phiext_full' Solve GK equation with additional source proportional to phi_ext*F_0.
• 'test2_full' Solve GK equation with additional developmental sources included. Experts only.
• 'convect_full' Solve GK equation with additional developmental sources included. Experts only.
• 'test1' The GK distribution function will be advanced non-self-consistently.
t0 Float -1.0,100.0 t0
• Turn on any artificial sources after time t0.

kt_grids_range_parameters

Name Type Def CR Name Description
akx_max Float akx_max
• Max kx for periodic finite kx ballooning space runs with $\hat{s}$=0.
akx_min Float 0.0 akx_min
• Min kx for periodic finite kx ballooning space runs with $\hat{s}=0$.
aky_max Float 1.0 aky_max
• Upper limit of (ky rho) range. Should set to something other than zero.
aky_min Float 0.0 aky_min
• Lower limit of (ky rho) range. Should set to something other than zero.
kyspacing_option String kyspacing_option
• Sets the type of spacing between ky grid points, available options are :
• 'default'  : Same as 'linear'
• 'exponential' : Evenly spaced in log(ky).
• 'linear' : Evenly spaced in ky.
n0_max Integer n0_max
• Maximum toroidal mode number.
  If n0_min > 0 then
if (mod(n0_max-n0_min,nn0).ne.0 .or. nn0 .eq. 1 .or. n0_min.ge.n0_max) then
set naky=1, aky_max=aky_min
else
set naky=nn0, aky_max=n0_max*drhodpsi*rhostar_range
endif

n0_min Integer 0 n0_min
• Minimum toroidal mode number.
  if n0_min > 0 then
set aky_min=n0_min*drhodpsi*rhostar_range
endif

naky Integer 1 naky
• The number of 'actual' ky modes.
nn0 Integer 1 nn0
• Number of toroidal modes, only used if n0_min>0. Overrides naky in kt_grids_range_parameters.
ntheta0 Integer lntheta0,ntheta0_private,size(akx) ntheta0
• Number of theta_0 (kx) modes
rhostar_range Float 0.0001 rhostar_range
theta0_max Float theta0_max
• Upper limit of theta_0 range
theta0_min Float 0.0 theta0_min
• Lower limit of theta_0 range

kt_grids_specified_parameters

Name Type Def CR Name Description
naky Integer 1 naky
• Number of ky values evolved. Total number of modes evolved = max(naky, ntheta0). Also set up the appropriate number of kt_grids_specified_element_i namelists.
ntheta0 Integer lntheta0,ntheta0_private,size(akx) ntheta0
• Number of theta0 values. Total number of modes evolved = max(naky, ntheta0). Also set up the appropriate number of kt_grids_specified_element_i namelists.
nx Integer 0 nx
ny Integer ny_private,yxf_lo%ny ny

kt_grids_specified_element

There should be a separate namelist for each Fourier mode. For example, if there are two modes, there will be namelists called kt_grids_specified_element_1 and kt_grids_specified_element_2.

Name Type Def CR Name Description
akx Float 0.0 akx
aky Float 0.4 aky
• ky rho
theta0 Float 0.0 theta0
• theta_0

kt_grids_xbox_parameters

Name Type Def CR Name Description

gs2_flux_knobs

Name Type Def CR Name Description

flux_target

Name Type Def CR Name Description

parameter_scan_knobs

Name Type Def CR Name Description
delta_t_inc Float 0.0 delta_t_inc
• When the increment condition is 'delta_t', the parameter will be changed every time delta_t time has elapsed.
delta_t_init Float 0.0 delta_t_init
• When the increment condition is 'delta_t', the parameter will not be changed until delta_t_init time has elapsed from the beginning of the simulation. Note, that if the simulation is restarted, this parameter will measure from beginning of original simulation.
inc_con String delta_t inc_con
• Specifies the condition for incrementing the parameter. Possible values are:
• 'n_timesteps' -- change the parameter after a given number of time steps
• 'delta_t' -- change the parameter after an elapsed time
• 'saturated' -- change the parameter after the simulation has reached a saturated state (determined using the target parameter) at the current value of the parameter
nstep_inc Integer 0 nstep_inc
• When the increment condition is 'n_timesteps', the parameter will be changed every nstep_inc.
nstep_init Integer 0 nstep_init
• When the increment condition is 'n_timesteps' or 'saturated', the parameter will not be changed until nstep_init have elapsed from the beginning of the simulation. Note that if the simulation is restarted, this parameter will measure from the restart.
par_end Float 0.0 par_end
• If the scan is being run in 'range' mode, specifies the value of the parameter that will be reached.
par_inc Float 0.0 par_inc
• If the parameter scan is being run in 'range' or 'target' modes, specifies the amount by which the parameter is varied at one go.
par_start Float 0.0 par_start
• Specifies the starting value for the parameter scan.
scan_par String tprim scan_par
• Specify the parameter to be varied. If the parameter pertains to a species, the scan_spec must be specified as well.
scan_restarted Fortran_Bool .false. scan_restarted
• Must be set to true if the current value of the scan parameter must be read from the restart files. Otherwise, the scan will start from the beginning.
scan_spec Integer 1 scan_spec
• When parameter pertains to a species, specifies the index of the species.
scan_type String none scan_type
• Specifies the way that the parameter scan is conducted. Possible values are:
• 'none' -- do not conduct a parameter scan (default)
• 'range' -- vary parameter in constant increments between 2 values: par_start and par_end. The step size is given by par_inc.
• 'target' -- start with the parameter at par_start, and then change the parameter by par_inc until the target parameter has reached the target value
• 'root_finding' -- the same as target, but the increment is changed intelligently using a Newton-like method.
target_par String hflux_tot target_par
• If the scan is being run in 'target' or 'root_finding' mode, specifies the target parameter.
• Possible values are 'hflux_tot', 'momflux_tot', 'phi2_tot'.
target_val Float 0.0 target_val
• If the scan is being run in 'target' or 'root_finding' mode, specifies the value to be targeted. The scan will complete when this target value is reached.

general_f0_parameters

Name Type Def CR Name Description
alpha_f0 String alpha_f0
• The distribution function for alphas can be "maxwellian", or it can be "analytic" based on a formula generated for the Ti=Te case, or it can be "external", i.e. read from an external table.
beam_f0 String beam_f0
• See help for alpha_f0
energy_0 Float energy_0
• Lower limit of the alpha distribution function for : F_alpha(energy_0)=0.
energy_min Float energy_min
• Garbage!
main_ion_species Integer main_ion_species
• Select the main ion species which will be used to generate the analytical F0.
print_egrid Fortran_Bool print_egrid
• Diagnostic: when true print the energy grid and generalised temperature.
rescale_f0 Fortran_Bool rescale_f0
• When reading the distribution function from an external table, rescale to a specified density if true.

diagnostics_config

This namelists controls the behaviour of the new diagnostics module (which can be enabled by setting USE_NEW_DIAG=on).

Name Type Def CR Name Description
conv_max_step Integer conv_max_step
conv_min_step Integer conv_min_step
conv_nstep_av Integer conv_nstep_av
conv_nsteps_converged Integer conv_nsteps_converged
conv_test_multiplier Float conv_test_multiplier
dump_fields_periodically Fortran_Bool dump_fields_periodically
• Phi, Apar, Bpar written to dump.fields.t=(time). This is expensive!
enable_parallel Fortran_Bool enable_parallel
• If built with parallel IO capability, enable it. There are currently issues with parallel IO on some systems which cause GS2 to hang. If you enable this parameter, test it on a smaller problem (but with at least two nodes) before using it on a prouction run. Bug reports welcome.
exit_when_converged Fortran_Bool .true. exit_when_converged
• If .true. when the frequencies for each k have converged, the run will stop.
igomega Integer 0 igomega
• Theta index at which frequencies are calculated.
navg Integer 10,100 navg
• Any time averages (for example growth rates and frequencies) performed over navg timesteps
ncheck Integer ncheck
• If vary_vnew, check to see whether to vary the collisionality every ncheck timesteps.
nwrite_large Integer nwrite_large
• Not in use currently
nwrite Integer 10,100 nwrite_new
• Diagnostic quantities are written every nwrite timesteps.
omegatinst Float 1.0,1000000.0 omegatinst
• If any growth rate is greater than omegatinst, assume there is a numerical instability and abort.
omegatol Float -0.001 omegatol
• In linear runs GS2 will exit if the growth rate has converged to an accuracy of one part in 1/omegatol. Set negative to switch off this feature.
print_flux_line Fortran_Bool print_flux_line
• Instantaneous fluxes output to screen every nwrite timesteps
print_line Fortran_Bool print_line
• Estimated frequencies and growth rates output to the screen/stdout every nwrite timesteps
save_distfn Fortran_Bool save_distfn
• If true, saves the restart files with name 'rootname.nc.dfn.<proc>' with lots of extra detail about the dist function --- velocity space grids and so on, when GS2 exits.
save_for_restart Fortran_Bool save_for_restart
• If true then restart files written to the local folder and the simulation can be restarted from the point it ended.
• Restart files written to restart_file.PE#.
• Recommended for nonlinear runs.
serial_netcdf4 Fortran_Bool serial_netcdf4
use_nonlin_convergence Fortran_Bool use_nonlin_convergence
write_any Fortran_Bool .true. write_any
• If .false. disables the new diagnostics module. No output is written.
write_apar_over_time Fortran_Bool .false. write_apar_over_time
• If this variable is set to true then the entire field apar will be written to the NetCDF file every nwrite. Useful for making films. This can cause the NetCDF file to be huge, if resolution is large or nwrite is small.
write_ascii Fortran_Bool write_ascii
• Controls the creation of a large number of ascii data files (such as <run_name>.new.fields). Many of diagnostics will write to ascii files as well as the netdf file if this flag is true.
write_bpar_over_time Fortran_Bool .false. write_bpar_over_time
• If this variable is set to true then the entire field bpar will be written to the NetCDF file every nwrite. Useful for making films. This can cause the NetCDF file to be huge, if resolution is large or nwrite is small.
write_cerr Fortran_Bool write_cerr
write_correlation Fortran_Bool write_correlation
• Write correlation function diagnostic... shows parallel correlation as a function of ky. See arXiv 1104.4514.
write_correlation_extend Fortran_Bool write_correlation_extend
• If used in conjunction with write_correlation, extends the length of $\Delta \theta$ for which the correlation function is calculated.
write_cross_phase Fortran_Bool write_cross_phase
• Write cross phase between electron temperature and density.
write_density_over_time Fortran_Bool write_density_over_time
• Write non-adiabitic density as a function theta, ky, kx, species and time... very expensive!
write_eigenfunc Fortran_Bool write_eigenfunc
• If (write_ascii = T) Normalized Phi(theta) written to runname.eigenfunc
• Write to runname.out.nc even if (write_ascii = F)
write_fields Fortran_Bool .false.,.true. write_fields
• If .true. write out values of phi, apar and bpar.
write_final_antot Fortran_Bool write_final_antot
• If (write_ascii = T) Sources for Maxwell eqns. written to runname.antot
• Write to runname.out.nc even if (write_ascii = F)
write_final_db Fortran_Bool write_final_db
• Write final delta B.
write_final_epar Fortran_Bool write_final_epar
• If (write_ascii = T) E_parallel(theta) written to runname.eigenfunc
• Write to runname.out.nc even if (write_ascii = F)
write_final_fields Fortran_Bool write_final_fields
• If (write_ascii = T) Phi(theta) written to runname.fields
• Write to runname.out.nc even if (write_ascii = F)
write_final_moments Fortran_Bool write_final_moments
• If (write_ascii = T) low-order moments of g written to runname.moments and int dl/B averages of low-order moments of g written to runname.amoments
• Write to runname.out.nc even if (write_ascii = F)
write_flux_line Fortran_Bool write_flux_line
• Instantaneous fluxes output to runname.new.out every nwrite timesteps (regardless of the value of write_ascii)
write_fluxes Fortran_Bool .true. write_fluxes
• If .true. write fluxes of heat, momentum & particles to the new netcdf file.
write_fluxes_by_mode Fortran_Bool .false. write_fluxes_by_mode
• If .true., write fluxes as a function of ky, kx, species and time (otherwise they will only be written out as functions of species, time and kx or ky). Creates large output files.
write_full_moments_notgc Fortran_Bool write_full_moments_notgc
write_g Fortran_Bool write_g
• Write the distribution function (in fourier space) at a fixed wavenumber to the '.dist' file
write_gs Fortran_Bool write_gs
write_gyx Fortran_Bool write_gyx
• Write dist fn (in real space) at a given physical spacial point to a file
write_heating Fortran_Bool write_heating
• Write multiple diagnostics of turbulent heating and free energy generation and dissipation.
write_jext Fortran_Bool write_jext
• Write the external current in the antenna if enabled.
write_kpar Fortran_Bool write_kpar
• Spectrum in k_parallel calculated and written. Only works for periodic boundary??
write_line Fortran_Bool write_line
• Write estimated frequencies and growth rates to the output file (usually runname.new.out) every nwrite steps (regardless of the value of write_ascii).
write_lorentzian Fortran_Bool write_lorentzian
• Frequency Sweep Data
write_lpoly Fortran_Bool write_lpoly
• computes and returns lagrange interpolating polynomial for g. Needs checking.
write_max_verr Fortran_Bool write_max_verr
• Write the spatial index corresponding to the maximum error in the velocity space integrals
write_moments Fortran_Bool write_moments
• If true then we write the various velocity moments (density, parallel flow, temperature) of the distribution function to the netcdf file every nwrite steps.
write_movie Fortran_Bool write_movie
• Write fields in real space as a function of time. Note this uses transform2 and so includes the aliased gridpoints in the real space dimensions. This means that there is 30% reduncancy in the output. Consider writing the fields in k space as a function of time and doing the Fourier transforms in post processing
write_ntot_over_time Fortran_Bool write_ntot_over_time
• Write total density as a function theta, ky, kx, species and time... very expensive!
write_omega Fortran_Bool .false.,.true. write_omega
• If true writes omega (both growth rate and frequency) to netcdf file every nwrite timesteps.
• Also writes out omegaavg (omega averaged over navg steps) to netcdf file.
write_parity Fortran_Bool write_parity
• Writes parities in dist fn and particle fluxes
write_phi_over_time Fortran_Bool .false. write_phi_over_time
• If this variable is set to true then the entire field phi will be written to the NetCDF file every nwrite. Useful for making films. This can cause the NetCDF file to be huge, if resolution is large or nwrite is small.
write_symmetry Fortran_Bool write_symmetry
• Switch on a diagnostic to test the symmetry properties of the GK eqn. It calculates the momentum flux as a function of vpar, theta, and time.
write_tperp_over_time Fortran_Bool write_tperp_over_time
• Write perpendicular temperature perturbation as a function theta, ky, kx, species and time... very expensive!
write_upar_over_time Fortran_Bool write_upar_over_time
• Write parallel flow perturbation as a function theta, ky, kx, species and time... very expensive!
write_verr Fortran_Bool write_verr
• Write velocity space diagnostics to netcdf file and (if write_ascii) '.new.lpc' and '.new.vres' files. Clear documentation of the outputs is given in the netcdf file.

eigval_knobs

Name Type Def CR Name Description
extraction_option String default extraction_option
• Sets the extraction technique, must be one of:
• 'default' (use SLEPC default)
• 'slepc_default' (use SLEPC default)
• 'ritz'
• 'harmonic'
• 'harmonic_relative'
• 'harmonic_right'
• 'harmonic_largest'
• 'refined'
• 'refined_harmonic'
max_iter Integer PETSC_DECIDE max_iter
• Sets the maximum number of SLEPC iterations used.
• If not set (recommended) then let SLEPC decide what to use (varies with different options).
n_eig Integer 1 n_eig
• The number of eigenmodes to search for. number of modes found may be larger than this.
• How many GS2 timesteps to take each time SLEPc wants to advance the distribution function. Useful to separate closely spaced eigenvalues without changing delt.
save_restarts Fortran_Bool save_restarts
• If true then we save a set of restart files for each eigenmode found. These are named as standard restart file (i.e. influenced by the restart_file input), but have eig_<id> appended near end, where <id> is an integer representing the eigenmode id.
• If save_distfn of gs2_diagnostics_knobs is true then will also save the distribution function files.
solver_option String default solver_option
• Sets the type of solver to use, must be one of:
• 'default' (Krylov-Schur)
• 'slepc_default' (Krylov-Schur)
• 'power'
• 'subspace'
• 'arnoldi'
• 'lanczos'
• 'krylov'
• 'GD'
• 'JD'
• 'RQCG'
• 'CISS'
• 'lapack'
• 'arpack'
• 'blzpack'
• 'trlan'
• 'blopex'
• 'primme'
• 'feast'
• Not all solver types are compatible with other eigenvalue options, some options may not be supported in older SLEPC versions and some may require certain flags to be set when SLEPC is compiled.
targ_im Float 0.5 targ_im
• Imaginary part of the eigenvalue target
• Often beneficial to set this fairly large (e.g. 10)
targ_re Float 0.5 targ_re
• Real part of the eigenvalue target
• Often beneficial to set this fairly small (e.g. ~0)
tolerance Float 1.0e-06 tolerance
• Sets tolerance on SLEPC eigenmode search.
transform_option String default transform_option
• Sets the type of spectral transform to be used. Must be one of
• 'default' (let SLEPC decide)
• 'slepc_default' (let SLEPC decide)
• 'shell'
• 'shift'
• 'invert'
• 'cayley'
• 'fold'
• 'precond' (not implemented)
• Not all options are available in all versions of the library.
use_ginit Fortran_Bool .false. use_ginit
• If true then provide an initial guess for the eigenmode based on using init_g routines to initialise g.
• Probably most useful with ginit_option='many' (etc.) to start an eigenvalue search from a previously obtained solution.
which_option String default which_option
• Sets SLEPC mode of operation (i.e. what sort of eigenvalues it looks for). Must be one of
• 'default' (equivalent to 'target_magnitude')
• 'slepc_default' (let SLEPC decide)
• 'largest_magnitude'
• 'smallest_magnitude'
• 'largest_real'
• 'smallest_real'
• 'largest_imaginary'
• 'smallest_imaginary'
• 'target_magnitude' (complex eigenvalue magnitude closest to magnitude of target)
• 'target_real'
• 'target_imaginary'
• 'all' (only some solver types, e.g. lapack)
• 'user' (will use a user specified function to pick between eigenmodes, note not currently implemented)

ballstab_knobs

This namelist can be used to control how the ideal ballooning stability calculations are performed.

Name Type Def CR Name Description
make_salpha Fortran_Bool .false. make_salpha
• Doesn't currently do anything.
n_shat Integer 1 n_shat
• How many shat values should be used in s-alpha type scans
shat_min Float shat shat_min
• The minimum value of shat to use in scans
shat_max Float shat shat_max
• The maximum value of shat to use in scans
n_beta Integer 1 n_beta
• How many beta_prime values should be used in s-alpha type scans
beta_mul Float 1.0 beta_mul
• The maximum beta_prime in scans is beta_prime_equib*beta_mul
beta_div Float 1.0 beta_div
• The minimum beta_prime in scans is beta_prime_equib/beta_div
diff Float 0. diff
• Numerical value, should usually by 0 or 1/3.