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A new method for extending solutions to the self-similar relativistic magnetohydrodynamic equations for black hole outflows

A new method for extending solutions to the self-similar relativistic magnetohydrodynamic equations for black hole outflows
A new method for extending solutions to the self-similar relativistic magnetohydrodynamic equations for black hole outflows

The paradigm in which magnetic fields play a crucial role in launching/collimating outflows in many astrophysical objects continues to gain support. However, semi-analytical models including the effect of magnetic fields on the dynamics and morphology of jets are still missing due to the intrinsic difficulties in integrating the equations describing a collimated, relativistic flow in the presence of gravity. Only few solutions have been found so far, due to the highly non-linear character of the equations together with the need to blindly search for singularities. These numerical problems prevented a full exploration of the parameter space. We present a new integration scheme to solve r-self-similar, stationary, axisymmetric magnetohydrodynamic (MHD) equations describing collimated, relativistic outflows crossing smoothly all the singular points (Alfvén point and modified slow/fast points). For the first time, we are able to integrate from the disc mid-plane to downstream of the modified fast point. We discuss an ensemble of jet solutions, emphasizing trends and features that can be compared to observables. We present, for the first time with a semi-analytical MHD model, solutions showing counter-rotation of the jet for a substantial fraction of its extent. We find diverse jet configurations with bulk Lorentz factors up to 10 and potential sites for recollimation between 103 and 107 gravitational radii. Such extended coverage of the intervals of quantities, such as magnetic-to-thermal energy ratios at the base or the heights/widths of the recollimation region, makes our solutions suitable for application to many different systems where jets are launched.

Black hole physics, Galaxies: jets, Methods: numerical, MHD stars: jets
0035-8711
4417-4435
Ceccobello, C.
726b1984-3064-4ec4-8f7f-c178b9bd2849
Cavecchi, Y.
939cba7d-c099-4d5a-a962-1fee916ea176
Heemskerk, M.H.M.
992336bc-3a45-43e8-a164-601c00827745
Markoff, S.
0abe5c33-f762-47ba-b537-448b9ba69799
Polko, P.
b9c1dfce-491b-46b3-b822-7a2c428d2ad3
Meier, D.
a1b2d18c-511a-4aa9-a1c9-0341ea9a25a8
Ceccobello, C.
726b1984-3064-4ec4-8f7f-c178b9bd2849
Cavecchi, Y.
939cba7d-c099-4d5a-a962-1fee916ea176
Heemskerk, M.H.M.
992336bc-3a45-43e8-a164-601c00827745
Markoff, S.
0abe5c33-f762-47ba-b537-448b9ba69799
Polko, P.
b9c1dfce-491b-46b3-b822-7a2c428d2ad3
Meier, D.
a1b2d18c-511a-4aa9-a1c9-0341ea9a25a8

Ceccobello, C., Cavecchi, Y., Heemskerk, M.H.M., Markoff, S., Polko, P. and Meier, D. (2018) A new method for extending solutions to the self-similar relativistic magnetohydrodynamic equations for black hole outflows. Monthly Notices of the Royal Astronomical Society, 473 (4), 4417-4435. (doi:10.1093/MNRAS/STX2567).

Record type: Article

Abstract

The paradigm in which magnetic fields play a crucial role in launching/collimating outflows in many astrophysical objects continues to gain support. However, semi-analytical models including the effect of magnetic fields on the dynamics and morphology of jets are still missing due to the intrinsic difficulties in integrating the equations describing a collimated, relativistic flow in the presence of gravity. Only few solutions have been found so far, due to the highly non-linear character of the equations together with the need to blindly search for singularities. These numerical problems prevented a full exploration of the parameter space. We present a new integration scheme to solve r-self-similar, stationary, axisymmetric magnetohydrodynamic (MHD) equations describing collimated, relativistic outflows crossing smoothly all the singular points (Alfvén point and modified slow/fast points). For the first time, we are able to integrate from the disc mid-plane to downstream of the modified fast point. We discuss an ensemble of jet solutions, emphasizing trends and features that can be compared to observables. We present, for the first time with a semi-analytical MHD model, solutions showing counter-rotation of the jet for a substantial fraction of its extent. We find diverse jet configurations with bulk Lorentz factors up to 10 and potential sites for recollimation between 103 and 107 gravitational radii. Such extended coverage of the intervals of quantities, such as magnetic-to-thermal energy ratios at the base or the heights/widths of the recollimation region, makes our solutions suitable for application to many different systems where jets are launched.

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Cavecchi A new method - Accepted Manuscript
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Accepted/In Press date: 29 September 2017
e-pub ahead of print date: 3 October 2017
Published date: 1 February 2018
Keywords: Black hole physics, Galaxies: jets, Methods: numerical, MHD stars: jets

Identifiers

Local EPrints ID: 420721
URI: https://eprints.soton.ac.uk/id/eprint/420721
ISSN: 0035-8711
PURE UUID: 858813e8-ff38-4d42-b7bb-379dd3d2465f

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Date deposited: 14 May 2018 16:30
Last modified: 13 Mar 2019 18:29

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Contributors

Author: C. Ceccobello
Author: Y. Cavecchi
Author: M.H.M. Heemskerk
Author: S. Markoff
Author: P. Polko
Author: D. Meier

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