2008MNRAS.385..841W

Three energy mechanisms invoking large-scale magnetic fields are incorporated in a model to explain jet production in black hole (BH) systems, i.e. the Blandford-Znajek (BZ), the magnetic coupling (MC) and the Blandford-Payne (BP) processes. These energy mechanisms can coexist in a BH accretion disc based on the magnetic field configurations constrained by the screw instability, provided that the BH spin and the power-law index indicating the variation of the magnetic field at an accretion disc are greater than some critical values. In this model the jets are driven by the BZ process in the Poynting flux regime and by the BP process in the hydromagnetic regime, being consistent with the spine/sheath jet structure observed in BH sources of stellar and supermassive size.