Large-amplitude Blazar Polarization Angle Swing as a Signature of Magnetic Reconnection

Abstract

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 nonthermal particles. However, so far there is little clear observational signatures of relativistic magnetic reconnection events in astrophysical systems. Blazars are relativistic magnetized plasma outflows from supermassive black holes. Their multi-wavelength flares may be powered by relativistic magnetic reconnection. The highly variable radiation and polarization signatures are well covered by multi-wavelength observation campaigns, making them ideal targets to examine the magnetic reconnection model. Recent observations have found that several blazar flares are accompanied by optical polarization angle swings which may be of as large amplitude as > 180 • , challenging existing theoretical models. In this paper, we present integrated particle-in-cell (PIC) and polarized radiation transfer simulations of magnetic reconnection events. We find that plasmoid coalescences in the reconnection layer can give rise to highly variable light curves, low and fluctuating polarization degree, and rotating polarization angle. In particular, large-amplitude polarization angle swings, similar to those observed during blazar flares, can be a unique signature of relativistic magnetic reconnection events.

Constraining the photon coupling of ultra-light dark-matter axion-like particles by polarization variations of parsec-scale jets in active galaxies

“…Refs. [78,79]: we do not know in advance whether these features are present or not. Therefore, assuming fully random values of EVPA based on the experimental error bars would be misleading: to imitate the ULDM effect in such MC sets, (i) periodic fluctuations should appear in various sources and (ii) their periods, by chance, should coincide.…”

Determining the Dominant Acceleration Mechanism during Relativistic Magnetic Reconnection in Large-scale Systems

“…Magnetic reconnection is a plasma process that rapidly unleashes energy stored in magnetic shear into various forms of particle kinetic energy. It has been discussed in solar and space environments (Kopp & Pneuman 1976;Phan et al 2000), laboratory experiments (Ji et al 1998), and recently in the context of highenergy astrophysics (de Gouveia dal Pino & Lazarian 2005;Giannios et al 2009;Arons 2012;Hoshino & Lyubarsky 2012;Zhang & Yan 2011;McKinney & Uzdensky 2012;Zhang et al 2015Zhang et al , 2018. There is strong observational evidence suggesting that reconnection is an efficient process for producing energetic particles in various heliophysics and astrophysical systems (Birn et al 2012;Krucker et al 2010;Øieroset et al 2002;Oka et al 2018;Gary et al 2018;Abdo et al 2011;Tavani et al 2011).…”

Blazar Optical Polarimetry: Current Progress in Observations and Theories

“…In recent years, it has been well studied, both analytically and numerically, that magnetic reconnection can explain the blazar spectra and light curves [88,[102][103][104][105]. Recently, [106] has combined PIC with polarized radiation transfer simulations to study the polarization signatures during reconnection. Very interestingly, magnetic reconnection can make strong polarization angle swings (see Figure 8).…”