Distribution of Faraday Rotation Measure in Jets from Active Galactic Nuclei II. Prediction from our Sweeping Magnetic Twist Model for the Wiggled Parts of AGN Jets and Tails

摘要

Distributions of Faraday rotation measure (FRM) and the projected magneticfield derived by a 3-dimensional simulation of MHD jets are investigated basedon our "sweeping magnetic twist model". FRM and Stokes parameters werecalculated to be compared with radio observations of large scale wiggled AGNjets on kpc scales. We propose that the FRM distribution can be used to discussthe 3-dimensional structure of magnetic field around jets and the validity ofexisting theoretical models, together with the projected magnetic field derivedfrom Stokes parameters. In the previous paper, we investigated the basicstraight part of AGN jets by using the result of a 2-dimensional axisymmetricsimulation. The derived FRM distribution has a general tendency to have agradient across the jet axis, which is due to the toroidal component of themagnetic field generated by the rotation of the accretion disk. In this paper,we consider the wiggled structure of the AGN jets by using the result of a3-dimensional simulation. Our numerical results show that the distributions ofFRM and the projected magnetic field have a clear correlation with the largescale structure of the jet itself, namely, 3-dimensional helix. Distributions,seeing the jet from a certain direction, show a good matching with those in apart of 3C449 jet. This suggests that the jet has a helical structure and thatthe magnetic field (especially the toroidal component) plays an important rolein the dynamics of the wiggle formation because it is due to a current-drivenhelical kink instability in our model.