A magnetohydrodynamical model for the formation of episodic jets |
| |
| Authors: | Feng Yuan Jun Lin Kinwah Wu Luis C Ho |
| |
| Institution: | Joint Institute for Galaxy and Cosmology (JOINGC) of SHAO and USTC, Key Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030, China;National Astronomical Observatories/Yunnan Observatory, Chinese Academy of Sciences, Kunming 650011, China;Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA;Mullard Space Science Laboratory, University College London, Holmbury St Mary, Surrey RH5 6NT;The Observatories of the Carnegie Institution of Washington, 813 Santa Barbara Street, Pasadena, CA 91101, USA |
| |
| Abstract: | Episodic ejection of plasma blobs has 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 disc 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 centre, the plasmoid can attain relativistic speeds in about 35 min. |
| |
| Keywords: | accretion accretion discs black hole physics MHD ISM: jets and outflow |
|
|
