  Drift-reduced plasma fluid models are commonly used in plasma physics for
analytics and simulations; however, the validity of such models must be
verified for the regions of parameter space in which tokamak plasmas exist. By
looking at the linear behaviour of drift-reduced and full-velocity models one
can determine that the physics lost through the simplification that the
drift-reduction provides is important in the core region of the tokamak. It is
more acceptable for the edge-region but one must determine specifically for a
given simulation if such a model is appropriate.
