A Stratification in Magnetic Field Structures The Radio Outflow in NGC 4151

The nature of radio outflows in radio-quiet (RQ) active galactic nuclei (AGN) remains poorly understood. In this study, we present kiloparsec-scale polarization observations of the Seyfert galaxy NGC 4151 using the Karl G. Jansky Very Large Array in B configuration at 3 and 10 GHz. We find that the inferred magnetic field (B-field) structures show a stratification: a “spine–sheath”-like structure, with fields perpendicular to the jet direction in the “spine” and parallel in the “sheath,” is observed in the higher-resolution (0 (Formula presented) .″ 5) image at 10 GHz. In addition, a “wind”-like component with B-fields perpendicular to the radio outflow is observed in the 3 GHz image (resolution 2″); this feature is prominent along the “receding” (eastern) jet direction. Rotation measure (RM) ranges from −230 to 250 rad m⁻² over the polarized regions, indicating a low electron density (10⁻³ to 10⁻² cm⁻³), tenuous medium surrounding the source causing Faraday rotation. A tentative RM gradient of +75 to −25 rad m⁻² is observed transverse to the northern “wind” component, suggestive of a helical B-field threading it. Based on an analysis of the available radio and X-ray data, we conclude that the stratified radio outflow in NGC 4151 is magnetically driven. The biconical radio “wind” is found to be massive (1050–3200 M_⊙) with a high mass outflow rate (0.01–0.03 M_⊙ yr⁻¹) but low in kinetic power (<0.01% of L_bol), making it less impactful for galactic-scale feedback. Our study suggests that RQ AGN may also host magnetically dominant jets and winds, even while their jets are smaller and weaker compared to radio-loud AGN.