Formation of helical current during coalescence of current loops in pair plasmas

The nonlinear stage of tearing instability in pair (electron-position) plas mas is investigated by three-dimensional relativistic electromagnetic PIC ( particle-in-cell) code. Two parallel currents formed in a current sheet due to the tearing instability attract each other and begin to coalesce throug h magnetic reconnection. During coalescence of current loops, it is shown t hat two interactive current loops become unstable against kinetic kink inst ability, resulting in the helical structure. It is also found that the stro ng magnetic flux along the current is generated at the same stage.