The original GLF23 model described in the 1996 Waltz
paper [1] uses the flux-surface-averaged
shear rate
in circular geometry with a multiplier of .
Here, *v*_{E} is the shear velocity equal to
.
Since then it was discovered that the rate
can often exceed the maximum linear growth rate in the
outer half of the plasma leading to the formation of
an unphysical transport barrier. This was remedied
by using a real geometry extension of
where the toroidal field in *v*_{E} is replaced by
[2].
Here, the factor typically rises
to 2-3 in the outer half of elongated plasmas, thus
reducing the rate in that region significantly.
The corresponding multiplier for the original (retuned)
models is which has
been found to be consistent with recent gyro-kinetic
simulations by Waltz. To use the real geometry
shear, set **bt_flag=1** in the namelist input.
The effective B-field is computed
internally in subroutine callglf2d.f.

Thu Feb 20 11:20:39 EST 2003