Kinetic beaming in radiative relativistic magnetic reconnection: a mechanism for rapid gamma-ray flares in jets

Mehlhaff, John; Werner, Gregory R.; Uzdensky, Dmitri; Begelman, Mitchell C.

doi:10.1093/mnras/staa2346

Cited by 29 publications

(63 citation statements)

References 120 publications

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“…Magnetic reconnection, an intermittent phenomenon that is known to accelerate particles very efficiently, is ubiquitous in such current sheets (Kagan et al 2015). It could also be responsible for variable VHE emission (Cerutti et al 2012;Christie et al 2019;Mehlhaff et al 2020). It is unclear how such a current sheet can affect the pair discharge mechanism, and what the relative contributions of the polar cap and the current sheet emissions are.…”

Section: Introductionmentioning

confidence: 99%

Synthetic gamma-ray light curves of Kerr black hole magnetospheric activity from particle-in-cell simulations

Crinquand

Cerutti

Dubus

et al. 2021

A&A

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Context. The origin of ultra-rapid flares of very high-energy radiation from active galactic nuclei remains elusive. Magnetospheric processes, occurring in the close vicinity of the central black hole, could account for these flares. Aims. Our aim is to bridge the gap between simulations and observations by synthesizing gamma-ray light curves in order to characterize the activity of a black hole magnetosphere, using kinetic simulations. Methods. We performed global axisymmetric 2D general-relativistic particle-in-cell simulations of a Kerr black hole magnetosphere. We included a self-consistent treatment of radiative processes and plasma supply, as well as a realistic magnetic configuration, with a large-scale equatorial current sheet. We coupled our particle-in-cell code with a ray-tracing algorithm in order to produce synthetic light curves. Results. These simulations show a highly dynamic magnetosphere, as well as very efficient dissipation of the magnetic energy. An external supply of magnetic flux is found to maintain the magnetosphere in a dynamic state, otherwise the magnetosphere settles in a quasi-steady Wald-like configuration. The dissipated energy is mostly converted to gamma-ray photons. The light curves at low viewing angle (face-on) mainly trace the spark gap activity and exhibit high variability. On the other hand, no significant variability is found at high viewing angle (edge-on), where the main contribution comes from the reconnecting current sheet. Conclusions. We observe that black hole magnetospheres with a current sheet are characterized by a very high radiative efficiency. The typical amplitude of the flares in our simulations is lower than is detected in active galactic nuclei. These flares could result from the variation in parameters external to the black hole.

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Section: Introductionmentioning

confidence: 99%

Synthetic gamma-ray light curves of Kerr black hole magnetospheric activity from particle-in-cell simulations

Crinquand

Cerutti

Dubus

et al. 2021

A&A

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“…In such environments, reconnection in the relativistic regime has become a promising explanation for high-energy emission, especially since particle-in-cell (PIC) simulations have convincingly demonstrated that, in addition to heating plasma, reconnection can accelerate a significant fraction of particles to very high energies, yielding a non-thermal power-law energy distribution of particles (e.g. Zenitani & Hoshino 2001, 2005a,b, 2007Jaroschek et al 2004;Lyubarsky & Liverts 2008;Liu et al 2011;Sironi & Spitkovsky 2011Bessho & Bhattacharjee 2012;Cerutti et al 2012bCerutti et al , 2013Cerutti et al , 2014aKagan, Milosavljević & Spitkovsky 2013;Guo et al 2014Guo et al , 2015Guo et al , 2016bGuo et al , a, 2019Dahlin, Drake & Swisdak 2015, 2017Nalewajko et al 2015;Sironi, Petropoulou & Giannios 2015;Sironi, Giannios & Petropoulou 2016;Werner et al 2016Werner et al , 2018Werner, Philippov & Uzdensky 2019;Werner & Uzdensky 2017;Ball, Sironi & Özel 2018, 2019Hakobyan, Philippov & Spitkovsky 2019;Hakobyan et al 2021;Li et al 2019;Schoeffler et al 2019;Guo et al 2020;Kilian et al 2020;Mehlhaff et al 2020;Sironi & Beloborodov 2020;Zhang, Sironi & Giannios 2021). High-energy non-thermal particle acceleration (NTPA) followed by synchrotron or i...…”

Section: Introductionmentioning

confidence: 99%

Reconnection and particle acceleration in three-dimensional current sheet evolution in moderately magnetized astrophysical pair plasma

Werner

Uzdensky

2021

J. Plasma Phys.

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Magnetic reconnection, a plasma process converting magnetic energy to particle kinetic energy, is often invoked to explain magnetic energy releases powering high-energy flares in astrophysical sources including pulsar wind nebulae and black hole jets. Reconnection is usually seen as the (essentially two-dimensional) nonlinear evolution of the tearing instability disrupting a thin current sheet. To test how this process operates in three dimensions, we conduct a comprehensive particle-in-cell simulation study comparing two- and three-dimensional evolution of long, thin current sheets in moderately magnetized, collisionless, relativistically hot electron–positron plasma, and find dramatic differences. We first systematically characterize this process in two dimensions, where classic, hierarchical plasmoid-chain reconnection determines energy release, and explore a wide range of initial configurations, guide magnetic field strengths and system sizes. We then show that three-dimensional (3-D) simulations of similar configurations exhibit a diversity of behaviours, including some where energy release is determined by the nonlinear relativistic drift-kink instability. Thus, 3-D current sheet evolution is not always fundamentally classical reconnection with perturbing 3-D effects but, rather, a complex interplay of multiple linear and nonlinear instabilities whose relative importance depends sensitively on the ambient plasma, minor configuration details and even stochastic events. It often yields slower but longer-lasting and ultimately greater magnetic energy release than in two dimensions. Intriguingly, non-thermal particle acceleration is astonishingly robust, depending on the upstream magnetization and guide field, but otherwise yielding similar particle energy spectra in two and three dimensions. Although the variety of underlying current sheet behaviours is interesting, the similarities in overall energy release and particle spectra may be more remarkable.

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“…Several works have explored the blazar spectra and light curves resulting from relativistic magnetic reconnection in the blazar emission environment (Deng et al 2016;Petropoulou et al 2016;Yuan et al 2016;Kagan et al 2016;Mehlhaff et al 2020;Christie et al 2020). Their results are consistent with typical obser-vations.…”

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confidence: 99%

Radiation and Polarization Signatures from Magnetic Reconnection in Relativistic Jets. I. A Systematic Study

Zhang

Giannios

et al. 2020

ApJ

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It is commonly believed that blazar jets are relativistic magnetized plasma outflows from supermassive black holes. One key question is how the jets dissipate magnetic energy to accelerate particles and drive powerful multi-wavelength flares. Relativistic magnetic reconnection has been proposed as the primary plasma physical process in the blazar emission region. Recent numerical simulations have shown strong acceleration of nonthermal particles that may lead to multi-wavelength flares. Nevertheless, previous works have not directly evaluated γ-ray signatures from first-principle simulations. In this paper, we employ combined particle-in-cell and polarized radiation transfer simulations to study multiwavelength radiation and optical polarization signatures under the leptonic scenario from relativistic magnetic reconnection. We find harder-when-brighter trends in optical and Fermi-LAT γ-ray bands as well as closely correlated optical and γ-ray flares. The optical polarization angle swings are also accompanied by γ-ray flares with trivial time delays. Intriguingly, we find highly variable synchrotron self Compton signatures due to inhomogeneous particle distributions during plasmoid mergers. This feature may result in fast γ-ray flares or orphan γ-ray flares under the leptonic scenario, complementary to the frequently considered mini-jet scenario. It may also infer neutrino emission with low secondary synchrotron flux under the hadronic scenario, if plasmoid mergers can accelerate protons to very high energy.

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Kinetic beaming in radiative relativistic magnetic reconnection: a mechanism for rapid gamma-ray flares in jets

Cited by 29 publications

References 120 publications

Synthetic gamma-ray light curves of Kerr black hole magnetospheric activity from particle-in-cell simulations

Synthetic gamma-ray light curves of Kerr black hole magnetospheric activity from particle-in-cell simulations

Reconnection and particle acceleration in three-dimensional current sheet evolution in moderately magnetized astrophysical pair plasma

Radiation and Polarization Signatures from Magnetic Reconnection in Relativistic Jets. I. A Systematic Study

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