TOPOLOGICAL TRANSFORMATIONS IN ISOLATED STRAIGHT MAGNETIC-FLUX TUBES

Reconnection in an isolated straight magnetic flux tube with all the f ield lines continuously twisted is investigated by a three-dimensional magnetohydrodynamic simulation. It is found that in the case of strai ght geometry, drastic topological changes and prominent burstlike ther mal energy release occur, even though no ambient untwisted magnetic he ld exists. Three distinct phases of magnetic reconnection are observed . The first one corresponds to rapid (in the Alfven transit timescale) kinking and splitting of the one initial flux tube into two topologic ally distinct well-bundled helical tubes. At the second phase these tu bes rapidly reconnect each other in such a way that the configuration suffers the Mobius transformation (inversion) when each of the tubes, being compactly bundled at one end, scatters to a thin shell surroundi ng another tube at the opposite end. During the third phase, the magne tic configuration becomes essentially knotted and topologically uncert ain, but the knots are then rapidly kicked off by reconnection with fu rther recurrence of two well-bundled tubes observed just after the spl it phase. An interesting feature of magnetic reconnection associated w ith multilayer fine structure of electric current with near-parallel r econnecting magnetic field lines is also observed in the simulation.