Spatial growth of current-driven instability in relativistic rotating jets and the search for magnetic reconnection

Abstract

Using the three-dimensional relativistic magnetohydrodynamic code RAISHIN, we investigated the influence of radial density profile on the spatial development of the current-driven kink instability along magnetized rotating, relativistic jets. For the purpose of our study, we used a non-periodic computational box, the jet flow is initially established across the computational grid, and a precessional perturbation at the inlet triggers the growth of the kink instability. We studied light as well as heavy jets with respect to the environment depending on the density profile. Different angular velocity amplitudes have been also tested. The results show the propagation of a helically kinked structure along the jet and relatively stable configuration for the lighter jets. The jets appear to be collimated by the magnetic field and the flow is accelerated due to conversion of electromagnetic into kinetic energy. We also identify regions of high current density in filamentary current sheets, indicative of magnetic reconnection, which are associated to the kink unstable regions and correlated to the decrease of the sigma parameter of the flow. We discuss the implications of our findings for Poynting-flux dominated jets in connection with magnetic reconnection process. We find that fast magnetic reconnection may be driven by the kink-instability turbulence and govern the transformation of magnetic into kinetic energy thus providing an efficient way to power and accelerate particles in AGN and gamma-ray-burst relativistic jets.