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Outflow from Hot Accretion Flows

Published online by Cambridge University Press:  21 February 2013

Feng Yuan ,
Defu Bu  and
Maochun Wu
Feng Yuan
Affiliation:
Shanghai Astronomical Observatory, CAS; Shanghai 200030, China email: [email protected]
Defu Bu
Affiliation:
Shanghai Astronomical Observatory, CAS; Shanghai 200030, China email: [email protected]
Maochun Wu
Affiliation:
Shanghai Astronomical Observatory, CAS; Shanghai 200030, China email: [email protected]
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Abstract

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Numerical simulations of hot accretion flows have shown that the mass accretion rate decreases with decreasing radius. Two models have been proposed to explain this result. In the adiabatic inflow-outflow solution (ADIOS), it is thought to be due to the loss of gas in outflows. In the convection-dominated accretion flow (CDAF) model, it is explained as because that the gas is locked in convective eddies. In this paper we use hydrodynamical (HD) and magnetohydrodynamical (MHD) simulations to investigate which one is physical. We calculate and compare various properties of inflow (gas with an inward velocity) and outflow (gas with an outward velocity). Systematic and significant differences are found. For example, for HD flows, the temperature of outflow is higher than inflow; while for MHD flows, the specific angular momentum of outflow is much higher than inflow. We have also analyzed the convective stability of MHD accretion flow and found that they are stable. These results suggest that systematic inward and outward motion must exist, i.e., the ADIOS model is favored. The different properties of inflow and outflow also suggest that the mechanisms of producing outflow in HD and MHD flows are buoyancy associated with the convection and the centrifugal force associated with the angular momentum transport mediated by the magnetic field, respectively. The latter mechanism is similar to the Blandford & Payne mechanism but no large-scale open magnetic field is required here. Possible observational applications are briefly discussed.

Keywords

accretionaccretion discsblack hole physicshydrodynamics
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 8 , Symposium S290: Feeding Compact Objects: Accretion on All Scales , August 2012 , pp. 86 - 89
Copyright
Copyright © International Astronomical Union 2013

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