  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.
