Three-dimensional reconnection of untwisted magnetic flux tubes

Understanding the reconnection of magnetic fields in flux tubes is of key importance for modeling solar activity and space weather. We are therefore studying this process via three-dimensional MHD simulations. We report here on a simulation of the collision of a pair of perpendicular, untwisted magnetic flux tubes. We find that the collision proceeds in four stages. First, on contact, the tubes flatten out into wide sheets. Second, they begin to reconnect and the tearing mode instability is excited in the reconnection region. Third, the nonlinear evolution of the tearing mode creates a pair of reconnected flux tubes. Finally, these flux tubes reconnect with each other to coalesce into a single flux tube.We then report on a pair of simulations exploring how this behavior changes when the speed of flux tube collision is increased and when the magnetic resistivity is increased. Subject headings:MHD — Sun: flares — Sun: magnetic fields On-line material:mpeg animation