The and trapped electron mode model
by Weiland et al[5] is implemented when
is set greater than 1.
When
, only the hydrogen equations are used
(with no trapped electrons or impurities) to compute only the
mode.
When
, trapped electrons are included,
but not impurities.
When
, a single species of impurity ions is
included as well as trapped electrons.
When
, the effect of collisions is included.
When
, parallel ion (hydrogenic) motion and
the effect of collisions are included.
When
, finite beta effects and collisions are
included.
When
, parallel ion (hydrogenic) motion,
finite beta effects, and the effect of collisions are included.
When
, parallel ion (hydrogenic and impurity) motion,
finite beta effects, and the effect of collisions are included.
Finite Larmor radius corrections are included in all cases.
Values of `lswitch(1)` greater than 11 are reserved for extensions
of this Weiland model.

The mode growth rate, frequency, and effective diffusivities are
computed in subroutine `weiland14`.
Frequencies are normalized by and diffusivities are
normalized by
.
The order of the diffusivity equations is
, , , , , ...
Note that the effective diffusivities can be negative.

The diffusivity matrix is given above.

The impurity density gradient scale length is defined as

The electron density gradient scale length is defined as

where and . For this purpose, all the impurity species are lumped together as one effective impurity species and all the hydrogen isotopes are lumped together as one effective hydrogen isotope.