The 3D behavior of a twisted flux tube expanding in the corona: reconnection, writhe and jets

We discuss some aspects of magnetic reconnection which could help in understanding many aspects of magnetic plasma interactions. We will show that the helical structure often observed in polar jets is a natural consequence of magnetic helicity conservation in 3D reconnection driven by a collision of two parts of an emerging flux tube within the single emerged loop. We perform 3D simulations by solving the time-dependent, ideal MHD equations with a uniform initial twist. We deduce that the emergence of highly twisted magnetic flux introduces several null points, which in turn causes reconnection between opposite directions of magnetic field within a single loop at nearest part and the release of the trapped twist in the form of a helical jet-like emission.