Magnetic Reconnection in a Sheared Magnetic Flux Tube: Slippage versus Tearing

Abstract:

The process of magnetic reconnection in a flux tube can occur in a time-stationary fashion as slippage reconnection or in a time-dependent manner, for example, tearing instability. However, it is not well known how a system can be set up to sustain slippage reconnection, whether there is a competition between slippage reconnection and time-dependent reconnection, and, if so, at which point a transition between the two occurs. To investigate this question, using a three-dimensional MHD simulation, we model the time evolution of a flux tube, which is subjected to a localized, rotational tangential plasma flow on one end. Moreover, we add a spatially localized resistive region in the center of our simulation box in order to permit dissipation and slippage of magnetic field. As a result, firstly, the Poynting flux injected by the boundary rotational flow propagates to the resistive region and dissipates there. Secondly, tearing instability occurs with slippage reconnection in the resistive region when the cross section of a flux tube is elliptical enough, although only slippage reconnection occurs there when it is circular. Finally, the horizontal magnetic field generated by tearing instability region propagates to the both sides of our simulation box, which are not resistive region. It is possible that these results can be applied to specific problems such as auroral acceleration or reconnection in highly twisted flux tubes in the solar atmosphere.