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

Abstract

We report that relativistic magnetic reconnection events may 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 that may have an amplitude as large as >180°, challenging existing theoretical models. In this Letter, we present integrated particle-in-cell 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. Lastly, in particular, large-amplitude polarization angle swings, similar to those observed during blazar flares, can be a unique signature of relativistic magnetic reconnection events.

Authors:

Zhang, Haocheng  ^[1];

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Li, Xiaocan  ^[2];

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Guo, Fan  ^[2];

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Giannios, Dimitrios ^[1]

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+ Show Author Affiliations

1. Purdue Univ., West Lafayette, IN (United States)
2. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

Publication Date:

2018-08-01

Research Org.:

Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

Sponsoring Org.:

USDOE Laboratory Directed Research and Development (LDRD) Program

OSTI Identifier:

1484652

Report Number(s):

LA-UR-18-24854
Journal ID: ISSN 2041-8213

Grant/Contract Number:  

89233218CNA000001

Resource Type:

Journal Article: Accepted Manuscript

Journal Name:

The Astrophysical Journal. Letters

Additional Journal Information:

Journal Volume: 862; Journal Issue: 2; Journal ID: ISSN 2041-8213

Publisher:

Institute of Physics (IOP)

Country of Publication:

United States

Language:

English

Subject:

79 ASTRONOMY AND ASTROPHYSICS; 70 PLASMA PHYSICS AND FUSION TECHNOLOGY