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Related papers: Radiative Signatures of Plasmoid-Dominated Reconne…

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Powerful flares from blazars with short ($\sim$ min) variability timescales are challenging for current models of blazar emission. Here, we present a physically motivated ab initio model for blazar flares based on the results of recent…

High Energy Astrophysical Phenomena · Physics 2016-09-07 Maria Petropoulou , Dimitrios Giannios , Lorenzo Sironi

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…

High Energy Astrophysical Phenomena · Physics 2022-01-26 Haocheng Zhang , Xiaocan Li , Dimitrios Giannios , Fan Guo , Hannes Thiersen , Markus Böttcher , Tiffany Lewis , Tonia Venters

Blazars are relativistic magnetized plasma outflows from supermassive black holes that point very close to our line of sight. Their emission is nonthermal dominated and highly variable across the entire electromagnetic spectrum.…

High Energy Astrophysical Phenomena · Physics 2020-10-14 Haocheng Zhang , Xiaocan Li , Dimitrios Giannios , Fan Guo , Yi-Hsin Liu , Lingyi Dong

Fast $\gamma$-ray variability in blazars remains a central puzzle in high-energy astrophysics, challenging standard shock acceleration models. Blazars, a subclass of active galactic nuclei (AGN) with jets pointed close to our line of sight,…

High Energy Astrophysical Phenomena · Physics 2025-11-26 Chandan Kumar Das , Bhargav Vaidya , Amit Shukla , Giancarlo Mattia , Karl Mannheim

Blazar emission models based on magnetic reconnection succeed in reproducing many observed spectral and temporal features, including the short-duration luminous flaring events. Plasmoids, a self-consistent by-product of the tearing…

High Energy Astrophysical Phenomena · Physics 2020-01-08 I. M. Christie , M. Petropoulou , L. Sironi , D. Giannios

Relativistic magnetic reconnection events can widely exist in magnetized plasmas in astrophysical systems. During this process, oppositely directed magnetic field lines reconnect and release magnetic energy, efficiently accelerating…

High Energy Astrophysical Phenomena · Physics 2018-08-08 Haocheng Zhang , Xiaocan Li , Fan Guo , Dimitrios Giannios

The exact mechanism for the production of fast $\gamma$-ray variability in blazars remains debated. Magnetic reconnection, in which plasmoids filled with relativistic particles and magnetic fields are formed, is a viable candidate to…

High Energy Astrophysical Phenomena · Physics 2021-05-06 Manuel Meyer , Maria Petropoulou , Ian Christie

Blazars are characterized by relativistic jets that are closely aligned with our line of sight. This results in relativistic beaming, making blazars among the most luminous extragalactic sources across the electromagnetic spectrum, from…

High Energy Astrophysical Phenomena · Physics 2025-07-14 Stamatios Ilias Stathopoulos , Maria Petropoulou

Rapid and luminous flares of non-thermal radiation observed in blazars require an efficient mechanism of energy dissipation and particle acceleration in relativistic active galactic nuclei (AGN) jets. Particle acceleration in relativistic…

High Energy Astrophysical Phenomena · Physics 2016-09-08 Krzysztof Nalewajko

Mildly-relativistic shocks that are embedded in colliding magnetohydrodynamic flows are prime sites for relativistic particle acceleration and production of strongly variable, polarized multi-wavelength emission from relativistic jet…

High Energy Astrophysical Phenomena · Physics 2020-01-08 Markus Boettcher , Matthew G Baring

Minute-timescale TeV flares have been observed in several blazars. The fast flaring requires compact regions in the jet that boost their emission towards the observer at an extreme Doppler factor of delta>50. For TeV photons to avoid…

High Energy Astrophysical Phenomena · Physics 2015-06-12 Dimitrios Giannios

The origin of extremely fast variability is one of the long-standing questions in the gamma-ray astronomy of blazars. While many models explain the slower, lower energy variability, they cannot easily account for such fast flares reaching…

High Energy Astrophysical Phenomena · Physics 2023-10-18 J. Jormanainen , T. Hovatta , I. M. Christie , E. Lindfors , M. Petropoulou , I. Liodakis

Order of magnitude variability has been observed in the blazar sub-class of Active Galactic Nuclei on minute timescales. These high-energy flares are often difficult to explain with shock acceleration models due to the small size of the…

High Energy Astrophysical Phenomena · Physics 2019-06-12 Paul J. Morris , William J. Potter , Garret Cotter

The evolution of the spectral energy distribution during flares constrains models of particle acceleration in blazar jets. The archetypical blazar BL Lac provided a unique opportunity to study spectral variations during an extended strong…

High Energy Astrophysical Phenomena · Physics 2023-03-15 S. Agarwal , B. Banerjee , A. Shukla , J. Roy , S. Acharya , B. Vaidya , V. R. Chitnis , S. M. Wagner , K. Mannheim , M. Branchesi

Magnetic reconnection is often considered as the primary particle acceleration mechanism in a magnetized blazar zone environment. The majority of radiation in the reconnection layer comes from plasmoids and their mergers. In particular,…

High Energy Astrophysical Phenomena · Physics 2024-06-18 Haocheng Zhang , Lingyi Dong , Dimitrios Giannios

We construct a numerical model of emission from minijets, localized flows driven by magnetic reconnection inside Poynting-flux-dominated jets proposed to explain the ultrafast variability of blazars. The geometrical structure of the model…

High Energy Astrophysical Phenomena · Physics 2015-05-19 Krzysztof Nalewajko , Dimitrios Giannios , Mitchell C. Begelman , Dmitri A. Uzdensky , Marek Sikora

Observations of gamma-ray-bursts and jets from active galactic nuclei reveal that the jet flow is characterized by a high radiative efficiency and that the dissipative mechanism must be a powerful accelerator of non-thermal particles.…

High Energy Astrophysical Phenomena · Physics 2015-05-20 Lorenzo Sironi , Maria Petropoulou , Dimitrios Giannios

Blobs, or quasi-spherical emission regions containing relativistic particles and magnetic fields, are often assumed ad hoc in emission models of relativistic astrophysical jets, yet their physical origin is still not well understood. Here,…

High Energy Astrophysical Phenomena · Physics 2016-08-17 L. Sironi , D. Giannios , M. Petropoulou

Magnetic reconnection drives a wide range of astrophysical phenomena, including geomagnetic storms, solar flares, and activity in blazars. However, direct measurement of key reconnection observables remains challenging due to the remote and…

High Energy Astrophysical Phenomena · Physics 2026-04-02 Sergey K. Ermakov , Michael Bussmann , Alexander Debus , Richard Pausch , Ulrich Schramm , René Widera , Klaus Steiniger

Several models have been suggested to explain the fast gamma-ray variability observed in blazars, but its origin is still debated. One scenario is magnetic reconnection, a process that can efficiently convert magnetic energy to energy of…

High Energy Astrophysical Phenomena · Physics 2021-09-20 J. Jormanainen , T. Hovatta , E. Lindfors , I. Christie , M. Petropoulou , I. Liodakis
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