Transport Simulation of Magnetohydrodynamic Effects in Tokamaks

Methods for incorporating magnetohydrodynamic equilibria and internal instabilities into tokamak transport codes are reviewed with emphasis on how the models may be extended to reactor plasmas. Instabilities are characterized from a computational view as being either intermittent or continuous modes. Intermittent disturbances are treated adiabatically whereas saturated instabilities can be handled through enhanced transport coefficients. The m = 1/n = 1 mode serves as an example of how the character of an instability can change as we proceed from low-beta resistive plasmas to high-beta collisionless plasmas. The implications for reactor thermal dynamics of finite-beta-induced transport are discussed in terms of Impurity Studies Experiment-B observations and analysis.