Black Hole Flares: Ejection of Accreted Magnetic Flux through 3D Plasmoid-mediated Reconnection

Abstract

Magnetic reconnection can power bright, rapid flares originating from the inner magnetosphere of accreting black holes. We conduct extremely high-resolution (5376 × 2304 × 2304 cells) general-relativistic magnetohydrodynamics simulations, capturing plasmoid-mediated reconnection in a 3D magnetically arrested disk for the first time. We show that an equatorial, plasmoid-unstable current sheet forms in a transient, nonaxisymmetric, low-density magnetosphere within the inner few Schwarzschild radii. Magnetic flux bundles escape from the event horizon through reconnection at the universal plasmoid-mediated rate in this current sheet. The reconnection feeds on the highly magnetized plasma in the jets and heats the plasma that ends up trapped in flux bundles to temperatures proportional to the jet’s magnetization. The escaped flux bundles can complete a full orbit as low-density hot spots, consistent with Sgr A* observations by the GRAVITY interferometer. Reconnection near the horizon produces sufficiently energetic plasma to explain flares from accreting black holes, such as the TeV emission observed from M87. The drop in the mass accretion rate during the flare and the resulting low-density magnetosphere make it easier for very-high-energy photons produced by reconnection-accelerated particles to escape. The extreme-resolution results in a converged plasmoid-mediated reconnection rate that directly determines the timescales and properties of the flare.

Second Scale Submillimeter Variability of Sagittarius A* during flaring activity of 2019: On the Origin of Bright Near Infrared Flares

“…Among the physical mechanisms proposed as possible origins of the NIR flares such as population of non-thermal electrons, magnetic reconnection and shocks (Dodds-Eden et al 2010;Ponti et al 2017;Yusef-Zadeh et al 2012;Yuan et al 2003), the one the most independent from accretion rate is magnetic reconnection (Ripperda et al 2020(Ripperda et al , 2021. We therefore suggest that the brightest NIR flares of Sgr A* are likely caused by magnetic reconnection.…”

A stable and causal model of magnetohydrodynamics

“…Regardless, our work shows that applying the BDNK method [27][28][29][30][31] to MHD can be accomplished successfully. 8 The model presented here can be used for studying 7 Our analysis of the equation of state of [4] was performed in the weak field limit in which signatures of anisotropy are small but significant. It would be interesting to also explore the strong field limit in which features of anisotropy are more salient.…”

“…4.1 and found that besides the 7 transport coefficients obtained via Kubo formulae, an additional 11 parameters are needed to ensure stable and causal linear perturbations at every angle θ. 7 We have not explored the region of parameter space in full generality and as such it is possible that causality and stability could be enforced with a reduced number of additional coefficients. Regardless, our work shows that applying the BDNK method [27][28][29][30][31] to MHD can be accomplished successfully.…”

“…The broad interest in MHD stems from the fact that it is the standard theory describing aspects of plasma physics [1], heavy-ion collisions [2], the large scale structure of the universe [3] and the dynamics of classes of black holes in particular regimes [4], to mention a few. In the specific context of astrophysics, modelling of relativistic plasmas is useful for understanding neutron star mergers [5], relativistic jets and flaring activity [6,7], besides black hole accretion [8,9]. Any novel insight into the structure and foundations of MHD is bound to have a wide range of applications.…”

Modeling general-relativistic plasmas with collisionless moments and dissipative two-fluid magnetohydrodynamics

“…short gamma-ray bursts in the case of stellar mass black holes formed in neutron star collisions (Abbott et al 2017), or in supermassive black hole accretion (Prieto et al 2016). Supermassive black holes, such as M87, feature intriguing flaring activity (Berge et al 2006), which has recently been related to large scale reconnection happening in the vicinity of the black hole (Porth et al 2021;Ripperda et al 2020;Nathanail et al 2020;Ripperda et al 2021a). Such reconnection events are, however, not limited to black holes, but will also occur in over twisted neutron star magnetospheres (Parfrey et al 2013).…”