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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

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

The multi-wavelength spectral and temporal variability observed in blazars set tight constraints on current theoretical emission models. Here, we investigate the relativistic magnetic reconnection process as a source of blazar emission in…

High Energy Astrophysical Phenomena · Physics 2018-12-04 I. M. Christie , M. Petropoulou , L. Sironi , D. Giannios

The optical radiation and polarization signatures in blazars are known to be highly variable during flaring activities. It is frequently argued that shocks are the main driver of the flaring events. However, the spectral variability…

High Energy Astrophysical Phenomena · Physics 2016-01-27 Haocheng Zhang , Wei Deng , Hui Li , Markus Böttcher

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

Blazars are highly variable active galactic nuclei which emit radiation at all wavelengths from radio to gamma-rays. Polarized radiation from blazars is one key piece of evidence for synchrotron radiation at low energies and it also varies…

We show that magnetic reconnection in a magnetically-dominated fast-cooling plasma can naturally produce bright flares accompanied by rotations in the synchrotron polarization vector. With particle-in-cell simulations of reconnection, we…

High Energy Astrophysical Phenomena · Physics 2020-07-30 David N. Hosking , Lorenzo Sironi

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

Relativistic jets from supermassive black holes are among the most powerful and luminous astrophysical systems in Universe. We propose that the open magnetic field lines through the black hole, which drive a strongly magnetized jet, may…

High Energy Astrophysical Phenomena · Physics 2021-01-13 Haocheng Zhang , Dimitrios Giannios

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

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

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

Relativistic shocks are one of the most plausible sites of the emission of strongly variable, polarized multi-wavelength emission from relativistic jet sources such as blazars, via diffusive shock acceleration (DSA) of relativistic…

High Energy Astrophysical Phenomena · Physics 2016-09-06 Markus Boettcher

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

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

A single measurement of linear polarization of a nonthermal source provides direct information about the mean direction and level of ordering of the magnetic field. Monitoring of the polarization in blazars, combined with millimeter-wave…

High Energy Astrophysical Phenomena · Physics 2015-06-23 Alan P. Marscher

The polarization signatures of the blazar emissions are known to be highly variable. In addition to small fluctuations of the polarization angle around a mean value, sometimes large (> 180^o) polarization angle swings are observed. We…

High Energy Astrophysical Phenomena · Physics 2015-06-24 Haocheng Zhang , Xuhui Chen , Markus Boettcher , Fan Guo , Hui Li

Identifying the physical mechanism driving blazar flares remains a central challenge in high-energy astrophysics. We show that the energy dependence of the standard deviation of the polarization angle variability ($\sigma_\text{PA}$)…

High Energy Astrophysical Phenomena · Physics 2026-04-30 Haocheng Zhang , Benjamin de Jonge , Manel Errando , Xiaocan Li , Fan Guo

The jet composition and energy dissipation mechanism of Gamma-ray bursts (GRBs) and Blazars are fundamental questions which remain not fully understood. One plausible model is to interpret the $\gamma$-ray emission of GRBs and optical…

High Energy Astrophysical Phenomena · Physics 2016-04-27 Wei Deng , Haocheng Zhang , Bing Zhang , Hui Li

Common models of blazars and gamma-ray bursts assume that the plasma underlying the ob- served phenomenology is magnetized to some extent. Within this context, radiative signatures of dissipation of kinetic and conversion of magnetic energy…

High Energy Astrophysical Phenomena · Physics 2015-06-03 P. Mimica , M. A. Aloy
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