Title: Particle acceleration in relativistic magnetic reconnection with strong inverse-Compton cooling in pair plasmas

Abstract

Particle-in-cell (PIC) simulations have shown that relativistic collisionless magnetic reconnection drives non-thermal particle acceleration (NTPA), potentially explaining high-energy (X-ray/γ-ray) synchrotron and/or inverse Compton (IC) radiation observed from various astrophysical sources. The radiation back-reaction force on radiating particles has been neglected in most of these simulations, even though radiative cooling considerably alters particle dynamics in many astrophysical environments where reconnection may be important. We present a radiative PIC study examining the effects of external IC cooling on the basic dynamics, NTPA, and radiative signatures of relativistic reconnection in pair plasmas. We find that, while the reconnection rate and overall dynamics are basically unchanged, IC cooling significantly influences NTPA: the particle spectra still show a hard power law (index ≥ -2) as in non-radiative reconnection, but transition to a steeper power law that extends to a cooling-dependent cut-off. The steep power-law index fluctuates in time between roughly -3 and -5. The time-integrated photon spectra display corresponding power laws with indices ≈-0.5 and ≈-1.1, similar to those observed in hard X-ray spectra of accreting black holes.

Authors:

Werner, Gregory R.  ^[1];

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Philippov, Alexander A. ^[2]; Uzdensky, Dmitri A. ^[1]

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1. Center for Integrated Plasma Studies, Physics Department, 390 UCB, University of Colorado, Boulder, CO 80309, USA
2. Astronomy Department, University of California, Berkeley, 601 Campbell Hall, Berkeley, CA 94720, USA

Publication Date:

Sat Aug 25 00:00:00 EDT 2018

Research Org.:

Univ. of Colorado, Boulder, CO (United States)

Sponsoring Org.:

USDOE Office of Science (SC); National Aeronautics and Space Administration (NASA); National Science Foundation (NSF); Ambrose Monell Foundation

OSTI Identifier:

1478128

Alternate Identifier(s):

OSTI ID: 1611046

Grant/Contract Number:  

SC0008409; NNX17AK57G; NNX16AB28G; AST-1411879; NAS803060.

Resource Type:

Published Article

Journal Name:

Monthly Notices of the Royal Astronomical Society: Letters

Additional Journal Information:

Journal Name: Monthly Notices of the Royal Astronomical Society: Letters Journal Volume: 482 Journal Issue: 1; Journal ID: ISSN 1745-3925

Publisher:

Royal Astronomical Society

Country of Publication:

United Kingdom

Language:

English

Subject:

79 ASTRONOMY AND ASTROPHYSICS; Astronomy & Astrophysics; acceleration of particles; accretion; accretion discs; magnetic reconnection; radiation mechanisms: general; galaxies: jets; X-rays: binaries