MHD simulations of jets from Keplerian disks: standing recollimation shocks
Creators: name: Jannaud, T.
name: Zanni, C.
name: Ferreira, J.
Publisher: name: Zenodo
Year: 2021
Subjects: Magnetohydrodynamics (MHD)
Methods: Numerical
ISM: Jets and outflows
Galaxies: Active

description: The most successful scenario to explain the origin of astrophysical jets requires the presence of a large-scale magnetic field anchored in a rotating object (black hole or disk) to extract its rotational energy and transfer it to the jet to accelerate it. Besides generating an accelerating force, the interplay of the large-scale magnetic field and the associated electric currents provides a confinement mechanism similar to Z-pinch systems, used for example to confine hot plasma in a tokamak. In order to provide a hoop stress able to compress the jet on such large scales, this Z-pinch requires a non-vanishing asymptotic electric current inside the jet. But linking this asymptotic current to the source remains a long standing pending issue. As a first step towards this goal, we performed a set of 2.5D MHD simulations of non-relativistic jets emitted from keplerian accretion disks, using the PLUTO code. In these platform simulations, the disk is a boundary condition and only the jet acceleration and collimation are self-consistently computed (e.g. Ouyed &amp; Pudritz 1997, Fendt<strong> </strong>2006, Ramsey &amp; Clarke 2019). Thanks to a novel numerical method, our simulations have been successfully carried out at unprecedented time and spatial scales, reaching a steady state up to a distance larger than 5000 times the inner disk radius. We found that standing recollimation shocks on the jet axis and body are systematically obtained for a certain set of parameters, as proposed in the Jet Emitting Disk self-similar calculations of Ferreira (1997) and discussed in, e.g, Polko et al. (2013). The influence of the launching parameters on <strong> </strong>the shocks is studied. Some astrophysical consequences on the collimation properties of AGN and X-ray binary jets will then be briefly discussed.
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