Electric Fields in a Tokamak
  With the establishment of vanishing net electrostatic fields in a toroidally symmetric tokamak at equilibrium [R. W. Johnson, to appear in Phys. Rev. D], one is left needing an explanation for the measurement of an apparent radial electric field in experiments. Two scenarios are proposed, depending on the type of measurement being considered. Indirect measurement via the radial equation of motion for an impurity species possibly measures that species' net radial viscous force, and direct measurement via the motional Stark effect might reveal electric fields generated by the shifting of the toroidal magnetic flux density. 
Robert W. Johnson