Equilibrium currents in stellarators

The equilibrium currents in stellarators are shown to be very sensitive to changes in the internal geometry of the plasma column. The second ''cosine'' harmonic of the longitudinal current density which is observed experimentally may be a consequence of an outward displacement of the column due to the finite plasma pressure. The longitudinal current which arises during rapid plasma heating is determined by the displacement and, to an even greater extent, by the elongation of the magnetic surfaces. Equations are derived to relate this current explicitly to the geometric characteristics. The current-excitation effect is a manifestation of a strong depencence of the rotational transform in a stellarator on the shape and relative positions of the magnetic surfaces. The relations derived in this study explain the nature of this dependence