Numerical observations of a simulated jet with a passive helical magnetic field

The numerical magnetohydrodynamical (MHD) code ZEUS has been used to compute a Mach 6 jet (relative to the internal sound speed) with a density ratio η = 0.1 (jet density to ambient density) which possesses a dynamically passive helical magnetic field (i.e., β = 2μ_0_p/B^2^ >> 1). The calculation is used to compute the Stokes I, Q, and U parameters along the line of sight for various orientations of the jet with respect to the observer and for various initial pitch angles for the helical magnetic field. Thus, the implications of a jet with a passive magnetic field can be discussed for the first time in terms of real observational parameters such as total intensity and linear polarization. Comparisons between these "numerical observations" and specific VLA radio jets are made and it is found that for the most part, observational properties of radio structures are consistent with a passive magnetic field. Observational signatures are identified which allow line-of-sight effects to be distinguished from physical effects such as magnetic field orientation. Some qualitative generalizations are drawn from the numerical observations, and applications are suggested to the classical double radio sources.