2004ApJ...600...88U

Using the numerical data of MHD simulation for active galactic nucleus (AGN) jets based on our ``sweeping magnetic twist model'', we calculated the Faraday rotation measure (FRM) and the Stokes parameters to compare with observations. We propose that the FRM distribution can be used to discuss the three-dimensional structure of magnetic field around jets, together with the projected magnetic field derived from the Stokes parameters. In the present paper, we assumed the basic straight part of the AGN jet and used the data of axisymmetric simulation. The FRM distribution that we derived has a general tendency to have gradient across the jet axis, which is due to the toroidal component of the helical magnetic field generated by the rotation of the accretion disk. This kind of gradient in the FRM distribution is actually observed in some AGN jets, which suggests a helical magnetic field around the jets and thus supports our MHD model. Following this success, we are now extending our numerical observation to the wiggled part of the jets, using the data of three-dimensional simulation based on our model, in an upcoming paper.