Mass transport and the bootstrap current from Ohm's law in steady-state tokamaks

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Abstract
In a Tokamak, magnetofluid-dynamic waves rapidly equilibrate pressure and toroidal field along magnetic surfaces. As a result, the detailed current distribution is determined by the flux surface averaged poloidal and toroidal currents. The portion of toroidal current driven by plasma outflow is identified with the bootstrap current. Given the toroidal current, the determination of the poloidal current, through Ohm's law, yields the plasma pressure. A combination of toroidal and poloidal Ohms's law, namely the component parallel to the magnetic field eliminates the influence of plasma fueling, and directly relates the bootstrap current and the pressure gradient. The latter is the usual relation, but, since it is infected with the uncertainties of the poloidal current drive, it is more problematic than the relation between bootstrap current and plasma fueling. In this paper the dependence of toroidal current and poloidal beta on various coefficients in Ohm's law is studied.