Black hole flares: ejection of accreted magnetic flux through 3D plasmoid-mediated reconnection

Ripperda, Bart; Liska, Matthew; Chatterjee, Koushik; Musoke, Gibwa; Philippov, Alexander A.; Markoff, Sera B.; Tchekhovskoy, Alexander; Younsi, Ziri

doi:10.48550/arxiv.2109.15115

Cited by 9 publications

(12 citation statements)

References 47 publications

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“…Dissipation, most likely caused by magnetic reconnection in current sheets near the midplane (e.g. Ripperda et al 2021), leads to localised heating of the plasma to temperatures of T i ∼ 10 12 K and T e ∼ 10 9 K, which suggest that electrons radiate their heat locally (see also Beloborodov 2017). A significant part of this heated plasma flows out as a wind along the magnetic field lines.…”

Section: Resultsmentioning

confidence: 99%

Formation of Magnetically Truncated Accretion Disks in 3D Radiation-Transport Two-Temperature GRMHD Simulations

Liska¹,

Musoke²,

Tchekhovskoy³

et al. 2022

Preprint

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Multi-wavelength observations suggest that the accretion disk in the hard and intermediate states of X-ray binaries (XRBs) and active galactic nuclei (AGN) transitions from a cold, thin disk at large distances into a hot, thick flow close to the black hole. However, the formation, structure and dynamics of such truncated disks are poorly constrained due to the complexity of the thermodynamic, magnetic, and radiative processes involved. We present the first radiation-transport two-temperature general relativistic magnetohydrodynamic (GRMHD) simulations of truncated disks radiating at ∼ 35% of the Eddington luminosity with and without large-scale poloidal magnetic flux. We demonstrate that when a geometrically-thin accretion disk is threaded by largescale net poloidal magnetic flux, it self-consistently transitions at small radii into a two-phase medium of cold gas clumps floating through a hot, magnetically dominated corona. This transition occurs at a well-defined truncation radius determined by the distance out to which the disk is saturated with magnetic flux. The average ion and electron temperatures in the semi-opaque corona reach, respectively, T i 10 10 K and T e 5 × 10 8 K. The system produces radiation, powerful collimated jets and broader winds at the total energy efficiency exceeding 90%, the highest ever energy extraction efficiency from a spinning black hole by a radiatively efficient flow in a GRMHD simulation. This is consistent with jetted ejections observed during XRB outbursts. The two-phase medium can naturally lead to broadened iron line emission observed in the hard state.

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Section: Resultsmentioning

confidence: 99%

Formation of Magnetically Truncated Accretion Disks in 3D Radiation-Transport Two-Temperature GRMHD Simulations

Liska¹,

Musoke²,

Tchekhovskoy³

et al. 2022

Preprint

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“…It is generally accepted that the mechanism regulating the saturation of 𝜙 BH in MADs involves the formation of highly magnetized, low-density bubbles near the black hole that rise buoyantly to larger radii, taking the flux away (Igumenshchev 2008;Tchekhovskoy et al 2011;McKinney et al 2012;Avara et al 2016;Marshall et al 2018;Porth et al 2021). As they rise the bubbles create an empty space near the black hole where the open magnetic field lines threading the black hole, which are associated with the jet, can reconnect (Igumenshchev et al 2003;Scepi et al 2021;Ripperda et al 2021). This reconnection effectively regulates the amount of magnetic flux threading the black hole.…”

Section: Time-dependent and Non-axisymmetric Behavior Of Mads: The Ro...mentioning

confidence: 99%

What really makes an accretion disc MAD

Begelman,

Scepi,

Dexter

2021

Preprint

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Magnetically arrested accretion discs (MADs) around black holes (BH) have the potential to stimulate the production of powerful jets and account for recent ultra-high-resolution observations of BH environments. Their main properties are usually attributed to the accumulation of dynamically significant net magnetic (vertical) flux throughout the arrested region, which is then regulated by interchange instabilities. Here we propose instead that it is mainly a dynamically important toroidal field -the result of dynamo action triggered by the significant but still relatively weak vertical field -that defines and regulates the properties of MADs. We suggest that rapid convection-like instabilities, involving interchange of toroidal flux tubes and operating concurrently with the magnetorotatonal instability (MRI), can regulate the structure of the disc and the escape of net flux. We generalize the convective stability criteria and disc structure equations to include the effects of a strong toroidal field and show that convective flows could be driven towards two distinct marginally stable states, one of which we associate with MADs. We confirm the plausibility of our theoretical model by comparing its quantitative predictions to simulations of both MAD and SANE (strongly magnetized but not "arrested") discs, and suggest a set of criteria that could help to distinguish MADs from other accretion states. Contrary to previous claims in the literature, we argue that MRI is not suppressed in MADs and is probably responsible for the existence of the strong toroidal field.

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“…The global picture of the reconnection processes taking place in the turbulent accretion environments near a black hole can be drawn only by exploiting accurate and long-term GRMHD simulations (Chan et al 2015;Dexter et al 2009;Dodds-Eden et al 2010;Ball et al 2016;Dexter et al 2020;Porth et al 2021;Ripperda et al 2021). Such simulations have recently provided a significant boost to the study and understanding of the occurrence and on the impact that magnetic reconnection has in accretion flows (Ball et al 2018a;Qian et al 2018;Kadowaki et al 2018;Vourellis et al 2019;White et al 2020;Čemeljić et al 2020;Dihingia et al 2021;Chashkina et al 2021;Scepi et al 2021).…”

Section: Introductionmentioning

confidence: 99%

Magnetic reconnection and plasmoid formation in three-dimensional accretion flows around black holes

Nathanail,

Mpisketzis,

Porth

et al. 2021

Preprint

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Magnetic reconnection is thought to be one of the main energy-dissipation mechanisms fueling energy to the plasma in the vicinity of a black hole. Indeed, plasmoids formed though magnetic reconnection may play a key role in γ-ray, X-ray and near-infrared flares from the black hole at the center of our galaxy, SgrA*. We report the results of three-dimensional general-relativistic ideal and resistive magnetohydrodynamics simulations modelling magnetic reconnection in accretion flows around astrophysical black holes. We show that current sheets are formed and destroyed rapidly in the turbulent environment of black-hole accretion. As this process operates, plasmoids are formed from the current sheets close to the event horizon and in a region of ∼ 2 −15 gravitational radii. We further quantify the magnetic dissipation and the process of energy transfer to the plasmoids, reporting the reconnection rate, the relative current density with respect to the local magnetic field, and the size of the plasmoids. We find that plasmoids gain energy through reconnection and heat up to relativistic temperatures, with the largest ones being sufficiently energetic to leave the black hole near the polar regions. During their evolution, plasmoids are stretched and elongated, becoming disrupted when the shear is sufficiently large, although some plasmoids survive as well-distinguished structures at distances of ∼ 30 − 40 gravitational radii from the black hole. Finally, we find that in some cases the plasmoids acquire a super-Keplerian azimuthal velocity, as suggested by recent observations of flares from Sgr A*.

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Black hole flares: ejection of accreted magnetic flux through 3D plasmoid-mediated reconnection

Cited by 9 publications

References 47 publications

Formation of Magnetically Truncated Accretion Disks in 3D Radiation-Transport Two-Temperature GRMHD Simulations

Formation of Magnetically Truncated Accretion Disks in 3D Radiation-Transport Two-Temperature GRMHD Simulations

What really makes an accretion disc MAD

Magnetic reconnection and plasmoid formation in three-dimensional accretion flows around black holes

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