TY - JOUR
T1 - Launching and quenching of black hole relativistic jets at low accretion rate
AU - Pu, Hung Yi
AU - Hirotani, Kouichi
AU - Chang, Hsiang Kuang
PY - 2012/10/20
Y1 - 2012/10/20
N2 - Relativistic jets are launched from black hole (BH) X-ray binaries and active galactic nuclei when the disk accretion rate is below a certain limit (i.e., when the ratio of the accretion rate to the Eddingtion accretion rate, ?m, is below about 0.01) but quenched when above. We propose a new paradigm to explain this observed coupling between the jet and the accretion disk by investigating the extraction of the rotational energy of a BH when it is surrounded by different types of accretion disk. At low accretion rates (e.g., when ?m ≲ 0.1), the accretion near the event horizon is quasi-spherical. The accreting plasmas fall onto the event horizon in a wide range of latitudes, breaking down the force-free approximation near the horizon. To incorporate the plasma inertia effect, we consider the magnetohydrodynamical (MHD) extraction of the rotational energy from BHs by the accreting MHD fluid, as described by the MHD Penrose process. It is found that the energy extraction operates, and hence a relativistic jet is launched, preferentially when the accretion disk consists of an outer ShakuraSunyaev disk (SSD) and an inner advection-dominated accretion flow. When the entire accretion disk type changes into an SSD, the jet is quenched because the plasmas bring more rest-mass energy than what is extracted from the hole electromagnetically to stop the extraction. Several other issues related to observed BH diskjet couplings, such as why the radio luminosity increases with increasing X-ray luminosity until the radio emission drops, are also explained.
AB - Relativistic jets are launched from black hole (BH) X-ray binaries and active galactic nuclei when the disk accretion rate is below a certain limit (i.e., when the ratio of the accretion rate to the Eddingtion accretion rate, ?m, is below about 0.01) but quenched when above. We propose a new paradigm to explain this observed coupling between the jet and the accretion disk by investigating the extraction of the rotational energy of a BH when it is surrounded by different types of accretion disk. At low accretion rates (e.g., when ?m ≲ 0.1), the accretion near the event horizon is quasi-spherical. The accreting plasmas fall onto the event horizon in a wide range of latitudes, breaking down the force-free approximation near the horizon. To incorporate the plasma inertia effect, we consider the magnetohydrodynamical (MHD) extraction of the rotational energy from BHs by the accreting MHD fluid, as described by the MHD Penrose process. It is found that the energy extraction operates, and hence a relativistic jet is launched, preferentially when the accretion disk consists of an outer ShakuraSunyaev disk (SSD) and an inner advection-dominated accretion flow. When the entire accretion disk type changes into an SSD, the jet is quenched because the plasmas bring more rest-mass energy than what is extracted from the hole electromagnetically to stop the extraction. Several other issues related to observed BH diskjet couplings, such as why the radio luminosity increases with increasing X-ray luminosity until the radio emission drops, are also explained.
KW - X-rays: binaries
KW - accretion, accretion disks
KW - black hole physics
KW - galaxies: active
KW - magnetic fields
KW - magnetohydrodynamics (MHD)
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U2 - 10.1088/0004-637X/758/2/113
DO - 10.1088/0004-637X/758/2/113
M3 - Article
AN - SCOPUS:84867298596
SN - 0004-637X
VL - 758
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 2
M1 - 113
ER -