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Title: Kinetic study of radiation-reaction-limited particle acceleration during the relaxation of unstable force-free equilibria

Abstract

Many powerful and variable gamma-ray sources, including pulsar wind nebulae, active galactic nuclei and gamma-ray bursts, seem capable of accelerating particles to gamma-ray emitting energies efficiently over very short timescales. These are likely due to the rapid dissipation of electromagnetic energy in a highly magnetized, relativistic plasma. In order to understand the generic features of such processes, we have investigated simple models based on the relaxation of unstable force-free magnetostatic equilibria. In this work, we make the connection between the corresponding plasma dynamics and the expected radiation signal, using 2D particle-in-cell simulations that self-consistently include synchrotron radiation reactions. We focus on the lowest order unstable force-free equilibrium in a 2D periodic box. We find that rapid variability, with modest apparent radiation efficiency as perceived by a fixed observer, can be produced during the evolution of the instability. The "flares" are accompanied by an increased polarization degree in the high energy band, with rapid variation in the polarization angle. Furthermore, the separation between the acceleration sites and the synchrotron radiation sites for the highest energy particles facilitates acceleration beyond the synchrotron radiation reaction limit. We also discuss the dynamical consequences of the radiation reaction, and some astrophysical applications of this model.more » Our current simulations with numerically tractable parameters are not yet able to reproduce the most dramatic gamma-ray flares, e.g., from the Crab Nebula. As a result, higher magnetization studies are promising and will be carried out in the future.« less

Authors:
ORCiD logo [1];  [2];  [1];  [1];  [1]
  1. SLAC National Accelerator Lab., Menlo Park, CA (United States)
  2. SLAC National Accelerator Lab., Menlo Park, CA (United States); Nicolaus Copernicus Astronomical Center, Warsaw (Poland)
Publication Date:
Research Org.:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1263399
Report Number(s):
SLAC-PUB-16753
Journal ID: ISSN 1538-4357; arXiv:1604.03179
Grant/Contract Number:
AC02-76SF00515
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
The Astrophysical Journal (Online)
Additional Journal Information:
Journal Name: The Astrophysical Journal (Online); Journal Volume: 828; Journal Issue: 2; Journal ID: ISSN 1538-4357
Publisher:
Institute of Physics (IOP)
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS; astrophysics; ASTRO; magnetic reconnection; acceleration of particles; radiation mechanisms: non-thermal; plasmas

Citation Formats

Yuan, Yajie, Nalewajko, Krzysztof, Zrake, Jonathan, East, William E., and Blandford, Roger D. Kinetic study of radiation-reaction-limited particle acceleration during the relaxation of unstable force-free equilibria. United States: N. p., 2016. Web. doi:10.3847/0004-637X/828/2/92.
Yuan, Yajie, Nalewajko, Krzysztof, Zrake, Jonathan, East, William E., & Blandford, Roger D. Kinetic study of radiation-reaction-limited particle acceleration during the relaxation of unstable force-free equilibria. United States. doi:10.3847/0004-637X/828/2/92.
Yuan, Yajie, Nalewajko, Krzysztof, Zrake, Jonathan, East, William E., and Blandford, Roger D. 2016. "Kinetic study of radiation-reaction-limited particle acceleration during the relaxation of unstable force-free equilibria". United States. doi:10.3847/0004-637X/828/2/92. https://www.osti.gov/servlets/purl/1263399.
@article{osti_1263399,
title = {Kinetic study of radiation-reaction-limited particle acceleration during the relaxation of unstable force-free equilibria},
author = {Yuan, Yajie and Nalewajko, Krzysztof and Zrake, Jonathan and East, William E. and Blandford, Roger D.},
abstractNote = {Many powerful and variable gamma-ray sources, including pulsar wind nebulae, active galactic nuclei and gamma-ray bursts, seem capable of accelerating particles to gamma-ray emitting energies efficiently over very short timescales. These are likely due to the rapid dissipation of electromagnetic energy in a highly magnetized, relativistic plasma. In order to understand the generic features of such processes, we have investigated simple models based on the relaxation of unstable force-free magnetostatic equilibria. In this work, we make the connection between the corresponding plasma dynamics and the expected radiation signal, using 2D particle-in-cell simulations that self-consistently include synchrotron radiation reactions. We focus on the lowest order unstable force-free equilibrium in a 2D periodic box. We find that rapid variability, with modest apparent radiation efficiency as perceived by a fixed observer, can be produced during the evolution of the instability. The "flares" are accompanied by an increased polarization degree in the high energy band, with rapid variation in the polarization angle. Furthermore, the separation between the acceleration sites and the synchrotron radiation sites for the highest energy particles facilitates acceleration beyond the synchrotron radiation reaction limit. We also discuss the dynamical consequences of the radiation reaction, and some astrophysical applications of this model. Our current simulations with numerically tractable parameters are not yet able to reproduce the most dramatic gamma-ray flares, e.g., from the Crab Nebula. As a result, higher magnetization studies are promising and will be carried out in the future.},
doi = {10.3847/0004-637X/828/2/92},
journal = {The Astrophysical Journal (Online)},
number = 2,
volume = 828,
place = {United States},
year = 2016,
month = 9
}

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  • A comparative analysis is performed of the electron emission characteristics as the electrons move in laser fields with ultra-relativistic intensity and different configurations corresponding to a plane or tightly focused wave. For a plane travelling wave, analytical expressions are derived for the emission characteristics, and it is shown that the angular distribution of the radiation intensity changes qualitatively even when the wave intensity is much less than that in the case of the radiation-dominated regime. An important conclusion is drawn that the electrons in a travelling wave tend to synchronised motion under the radiation reaction force. The characteristic features ofmore » the motion of electrons are found in a converging dipole wave, associated with the curvature of the phase front and nonuniformity of the field distribution. The values of the maximum achievable longitudinal momenta of electrons accelerated to the centre, as well as their distribution function are determined. The existence of quasi-periodic trajectories near the focal region of the dipole wave is shown, and the characteristics of the emission of both accelerated and oscillating electrons are analysed. (extreme light fields and their applications)« less
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  • The discharge flow technique was used to perform a direct measurement of the rate constant for the reaction NO/sub 3/ + Cl ..-->.. ClO + NO/sub 2/ (1) under pseudo-first-order conditions with NO/sub 3/ in excess. NO/sub 3/ was produced via the reaction F + HNO/sub 3/ ..-->.. HF + NO/sub 3/ (2) for which the rate constant was also determined: k/sub 2/ = (2.7 +/- 0.5) x 10/sup -11/ cm/sup 3/ molecule/sup -1/ s/sup -1/ at 298 K. Absolute titration of NO/sub 3/ was done using NO and 2,3-dimethyl-2-butene as the titrants. The titration experiments with NO were simulated,more » and the analysis of potential errors resulting from the secondary chemistry indicated that NO is a precise titrant of NO/sub 3/ in discharge flow studies. In the kinetic investigation of reaction 1, the obtained value of k/sub 1/ at 298 K was k/sub 1/ = (2.6 +/- 0.5) x 10/sup -11/ cm/sup 3/ molecule/sup -1/ s/sup -1/.« less