Remarks on the derivation and evaluation of the Stacey-Sigmar model for   tokamak equilibrium
  The Stacey-Sigmar model for tokamak equilibrium as presented in the literature relies heavily on the neoclassical theory of the electrostatic field. Its neglect of Gauss's law is inconsistent with the potential formulation of electrodynamics. Its treatment of the dynamic electric field generated by the central heating and poloidal field coils also is suspect. Its derivation of the viscosity term remains incomplete and does not account for the varying pitch angle of the magnetic field. A derivation of the viscosity term which respects the pitch angle can account for the radial force commonly ascribed to the radial electrostatic field, thereby obviating the desire to neglect Gauss's law. 
Robert W. Johnson
physics.plasm-ph