Topological Transformations in Isolated Straight Magnetic Flux Tubes

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Abstract
Reconnection in an isolated straight magnetic flux tube with all the field lines continuously twisted is investigated by a three-dimensional magnetohydrodynamic simulation. It is found that in the case of straight geometry, drastic topological changes and prominent burstlike thermal energy release occur, even though no ambient untwisted magnetic field exists. Three distinct phases of magnetic reconnection are observed. The first one corresponds to rapid (in the Alfvén transit timescale) kinking and splitting of the one initial flux tube into two topologically distinct well-bundled helical tubes. At the second phase these tubes rapidly reconnect each other in such a way that the configuration suffers the Möbius transformation (inversion) when each of the tubes, being compactly bundled at one end, scatters to a thin shell surrounding another tube at the opposite end. During the third phase, the magnetic configuration becomes essentially knotted and topologically uncertain, but the knots are then rapidly kicked off by reconnection with further recurrence of two well-bundled tubes observed just after the split phase. An interesting feature of magnetic reconnection associated with multilayer fine structure of electric current with near-parallel reconnecting magnetic field lines is also observed in the simulation.