Relativistic relationship between toroidal rotation and charge density in tokamaks

Relativity connects measured charge densities in tokamaks with toroidal rotation. Relativistic changes on charge density are of the order of the charge density itself, at least in the case of neutral beam injection. This needs to be taken into account when trying to understand the differences in electron and ion radial transport rates, reflected by the plasma charge. For instance, enhanced confinement in ISX-B associated with counter neutral beam injection happens to correspond to a locally less charged plasma, when compared to the corresponding co-injection case