A Multi-parameter Model for Radio Dichotomy of Active GalacticNuclei and Jets

Abstract

Based on the coexistence of the Blandford–Znajek andmagnetic coupling processes in black hole (BH) accretion disc,a multi-parameter model for jet powers and radio loudness of activegalactic nuclei (AGNs) is studied. It turns out that radio-loudness of AGNscould be governed by five parameters: (i) theBH spin, (ii) a power-law index of the variation of themagnetic field on the disc; (iii) a parameterdetermining the position of the inner edge of the disc, (iv)the ratio of the pressure of the magnetic field on the horizon tothe ram pressure of the innermost parts of an accretion flow,and (v) the ratio of the angularvelocity of the open field lines to that of the horizon. The observeddichotomy between radio-loud and radio-quiet AGNs is wellinterpreted by the effects of the above parameters. Furthermore, we discussthe derivative of radio loudness of AGNs with respect to each parameterseparately. In addition, the effect of the screw instability on radioloudness of AGNs is discussed.