A Magnetohydrodynamical Model for the Formation of Episodic Jets

Feng Yuan(1,2), Jun Lin(3,4), Kinwah Wu(5), and Luis C. Ho(6)

(1) Shanghai Astronomical Observatory, Shanghai 200030, China
(2) Joint Institute for Galaxy and Cosmology (JOINGC) of SHAO and USTC
(3) National Astronomical Observatories/Yunnan Observatory, Chinese Academy of Sciences, Kunming 650011, China
(4) Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
(5) Mullard Space Science Laboratory, University College London, Holmbury St Mary, Surrey RH5 6NT, UK
(6) The Observatories of the Carnegie Institution of Washington, 813 Santa Barbara Street, Pasadena, CA 91101, USA

Paper: MNRAS, 2009, 395, 2183

Weblink: http://www.shao.ac.cn/fyuan/yuan.html


Episodic ejection of plasma blobs have been observed in many black hole systems. While steady, continuous jets are believed to be associated with large-scale open magnetic fields, what causes the episodic ejection of blobs remains unclear. Here by analogy with the coronal mass ejection on the Sun, we propose a magnetohydrodynamical model for episodic ejections from black holes associated with the closed magnetic fields in an accretion flow. Shear and turbulence of the accretion flow deform the field and result in the formation of a flux rope in the disk corona. Energy and helicity are accumulated and stored until a threshold is reached. The system then loses its equilibrium and the flux rope is thrust outward by the magnetic compression force in a catastrophic way. Our calculations show that for parameters appropriate for the black hole in our Galactic center, the plasmoid can attain relativistic speeds in about 35 minutes.

Preprints available from the authors at fyuan@shao.ac.cn , or the raw TeX (no figures) if you click here.

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