Field-line reconnection and density fluctuations in Zeta

An outstanding problem in the behaviour of the Zeta plasma is the origin of the fluctuations of density; it has been shown experimentally that they do not arise directly from the observed turbulent motions of the plasma, and there is no known instability which can produce them directly. It is proposed that they arise as a by-product of resistive instabilities through their action in cross-connecting lines of force belonging to magnetic surfaces at different radii. This idea is developed quantitatively and it is shown that it predicts fluctuation levels in reasonable agreement with experiment. This result is interpreted as giving support to the 'tangled discharge' model of the zeta plasma. (author)