Magnetic field-line reconnexion by localised enhancement of resistivity

An examination is made as to how the process of fast reconnexion depends on the magnitude of the local resistivity enhanced in the vicinity of the magnetic neutral point. It is shown that quasi-steady Petschek-type configurations are set up, one for each of the variously imposed local resistivity enhancements. The fundamental structure of the quasi-steady configuration is largely controlled by the initially indented value of locally enhanced resistivity. It is seen that the magnitude of fast reconnexion rate has a weak dependence on the local resistivity in the diffusion region. All the numerical results are very consistent with previous theoretical work on the fast reconnexion problem, once the problem is reconsidered from another angle. It is suggested that the process of fast reconnexion should be viewed as a gross instability, inherent to the current sheet system itself, that can be triggered by some local onset of anomalous resistivity. (author)