This program is intended to serve as a stand-alone code
for testing the GLF23 model for Ion Temperature Gradient (ITG)
and Trapped Electron Mode (TEM) modes. The GLF23 model was
formulated by approximating the linear growth rates of the 3D
ballooning mode gyrokinetic (GKS) code whereby the transport
coefficients were taken from simulations of a 3D nonlinear
gyro-Landau-fluid (GLF) code [1]. The model contains
magnetic shear and Shafranov shift (
) stabilization
in addition to 
rotational shear stabilization.
It is a comprehensive transport model that predicts particle, electron
and ion thermal, toroidal momentum flows as well as turbulent
electron-ion energy exchange.
It is a dispersion type transport model similar in construction
to the fluid based Weiland ITG/TEM model where the diffusivities
are found by solving the complex eigenvalue problem
for a reduced set of perturbed
equations of motion. Here, 
is the eigenvalue and v is the corresponding
eigenvector. The current version of the model uses eight equations
(nroot = 8) and is electrostatic. The user has the option
to include impurity dynamics by setting nroot = 12, but
this is usually a small effect at low to moderate values of 
.
An internal eigenvalue solver (cgg) is incorporated
inside the main subroutine glf2d.f utilizing a sequence of routines
from the eispack package. The user has the option of using the
cgg solver (default) by setting leigen = 0 or using the more
modern tomsqz solver (leigen = 1).
The tomsqz routine has proven to be robust but solves
the generalized eigenvalue problem which makes it more computationally
intensive than the cgg eispack based solver. In our
experience, the cgg solver has proven reliable on
a number of platforms.
The eigenvalues yield the frequency and growth rates
of the modes while the eigenvectors give the phase of the perturbed
variables relative to one another.
A nonlinear saturation rule is used to compute the transport
for a spectrum of eigenmodes with 10 wavenumbers for the ion
temperature gradient (ITG) and trapped electron modes (TEM)
and 10 wavenumbers for the short wavelength electron temperature
gradient (ETG) modes. A mixing length formula is used
to give the heat diffusivity such that 
where
is the mode frequency, 
is radial mode
damping rate, and 
with 
denoting the mode growth
rate in the absence of rotational shear and with 
and
denoting the and diamagnetic rotational
shear rates, respectively.