RECONNECTION OF ANTIPARALLEL MAGNETIC-FLUX TUBES

Many examples of solar activity, such as large two-ribbon flares and p rominence eruptions, are widely believed to involve the fast reconnect ion of magnetic flux tubes. Because of the difficulties associated wit h calculating the evolution of three-dimensional (3-D) flux tubes, how ever, the details of the energy-release process are poorly understood. In this paper we describe our first attempts to shed light on this im portant process. We describe the results of 3-D numerical simulations of initially distinct magnetic flux tubes interacting via magnetic rec onnection. As a typical case, we consider an initial magnetic field gi ven by a compact support function distribution so that the initial top ology consists of two antiparallel flux tubes. We then impose an initi al velocity field on this system which causes the flux tubes to move t oward each other. As a result of this initial velocity, the tubes firs t flatten against each other and an electric current sheet begins to d evelop at the interface between them. After approximately 10 Alfven ti mes we observe a burst of reconnection. The turbulent kinetic energy r ises dramatically as two reconnection jets form, which are aligned par allel to the initial field. The reconnection phase lasts for approxima tely 20 Alfven times, by which time the central region of the initial tubes has been completely dissipated so that the system now consists o f four tubes that are relatively widely separated and hence stop inter acting. We find that the excitation of small-scale spatial structure i n the flow field depends critically on the value of the Lundquist numb ers. Compressible effects are insignificant for this particular case o f flux tube reconnection. The numerical simulations are carried out us ing a three-dimensional explicit Fourier collocation algorithm for sol ving the viscoresistive equations of compressible magnetohydrodynamics . We also report on the performance of a new parallelized version of t he code.