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Plasmoid formation in global GRMHD simulations and AGN flares

Nathanail, A; Fromm, CM; Porth, O; Olivares, H; Younsi, Z; Mizuno, Y; Rezzolla, L; (2020) Plasmoid formation in global GRMHD simulations and AGN flares. Monthly Notices of the Royal Astronomical Society , 495 (2) pp. 1549-1565. 10.1093/mnras/staa1165. Green open access

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Abstract

One of the main dissipation processes acting on all scales in relativistic jets is thought to be governed by magnetic reconnection. Such dissipation processes have been studied in idealized environments, such as reconnection layers, which evolve in merging islands and lead to the production of plasmoids, ultimately resulting in efficient particle acceleration. In accretion flows onto black holes, reconnection layers can be developed and destroyed rapidly during the turbulent evolution of the flow. We present a series of two-dimensional general-relativistic magnetohydrodynamic simulations of tori accreting onto rotating black holes focusing our attention on the formation and evolution of current sheets. Initially, the tori are endowed with a poloidal magnetic field having a multi-loop structure along the radial direction and with an alternating polarity. During reconnection processes, plasmoids and plasmoid chains are developed leading to a flaring activity and hence to a variable electromagnetic luminosity. We describe the methods developed to track automatically the plasmoids that are generated and ejected during the simulation, contrasting the behaviour of multi-loop initial data with that encountered in typical simulations of accreting black holes having initial dipolar field composed of one loop only. Finally, we discuss the implications that our results have on the variability to be expected in accreting supermassive black holes.

Type: Article
Title: Plasmoid formation in global GRMHD simulations and AGN flares
Open access status: An open access version is available from UCL Discovery
DOI: 10.1093/mnras/staa1165
Publisher version: http://dx.doi.org/10.1093/mnras/staa1165
Language: English
Additional information: This version is the version of record. For information on re-use, please refer to the publisher’s terms and conditions.
Keywords: accretion, accretion discs – black hole physics – magnetic reconnection.
UCL classification: UCL
UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Space and Climate Physics
URI: https://discovery.ucl.ac.uk/id/eprint/10101304
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