Magnetically Advected Winds

I Contopoulos; D Kazanas; K Fukumura

doi:10.1093/mnrasl/slx123

Magnetically Advected Winds

Mon Not R Astron Soc Lett. 2017 Nov;472(1):L20-L24. doi: 10.1093/mnrasl/slx123. Epub 2017 Aug 2.

Authors

I Contopoulos^{1

2}, D Kazanas³, K Fukumura⁴

Affiliations

¹ Research Centre for Astronomy and Applied Mathematics, Academy of Athens, Athens 11527, Greece.
² National Research Nuclear University, 31 Kashirskoe highway, Moscow 115409, Russia.
³ NASA Goddard Space Flight Centre, Greenbelt, MD 20771, USA.
⁴ Physics & Astronomy Department, James Madison University, Harrisonburg, VA 22840, USA.

Abstract

Observations of X-ray absorption lines in magnetically driven disc winds around black hole binaries and active galactic nuclei yield a universal radial density profile $ρ \propto r^{- 1.2}$ in the wind. This is in disagreement with the standard Blandford & Payne profile $ρ_{BP} \propto r^{- 1.5}$ expected when the magnetic field is neither advected nor diffusing through the accretion disc. In order to account for this discrepancy, we establish a new paradigm for magnetically driven astrophysical winds according to which the large scale ordered magnetic field that threads the disc is continuously generated by the Cosmic Battery around the inner edge of the disc and continuously diffuses outward. We obtain self-similar solutions of such magnetically advected winds (MAW) and discuss their observational ramifications.

Keywords: MHD; Magnetic Fields.