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Title: Efficient production of high-energy nonthermal particles during magnetic reconnection in a magnetically dominated ion-electron plasma

Magnetic reconnection is a leading mechanism for dissipating magnetic energy and accelerating nonthermal particles in Poynting-flux-dominated flows. We investigate nonthermal particle acceleration during magnetic reconnection in a magnetically dominated ion–electron plasma using fully kinetic simulations. For an ion–electron plasma with a total magnetization of $${\sigma }_{0}={B}^{2}/(4\pi n({m}_{i}+{m}_{e}){c}^{2})$$, the magnetization for each species is $${\sigma }_{i}\sim {\sigma }_{0}$$ and $${\sigma }_{e}\sim ({m}_{i}/{m}_{e}){\sigma }_{0}$$, respectively. We have studied the magnetically dominated regime by varying σe = 103–105 with initial ion and electron temperatures $${T}_{i}={T}_{e}=5-20{m}_{e}{c}^{2}$$ and mass ratio $${m}_{i}/{m}_{e}=1-1836$$. Our results demonstrate that reconnection quickly establishes power-law energy distributions for both electrons and ions within several (2–3) light-crossing times. For the cases with periodic boundary conditions, the power-law index is $$1\lt s\lt 2$$ for both electrons and ions. The hard spectra limit the power-law energies for electrons and ions to be $${\gamma }_{{be}}\sim {\sigma }_{e}$$ and $${\gamma }_{{bi}}\sim {\sigma }_{i}$$, respectively. The main acceleration mechanism is a Fermi-like acceleration through the drift motions of charged particles. When comparing the spectra for electrons and ions in momentum space, the spectral indices sp are identical as predicted in Fermi acceleration. We also find that the bulk flow can carry a significant amount of energy during the simulations. Finally, we discuss the implication of this study in the context of Poynting-flux dominated jets and pulsar winds, especially the applications for explaining nonthermal high-energy emissions.
Authors:
 [1] ;  [2] ;  [1] ;  [1] ;  [3] ;  [1] ;  [4] ;  [5] ;  [6]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  2. Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Univ. of Alabama, Huntsville, AL (United States). Dept. of Space Sciences
  3. Univ. of Nevada, Las Vegas, NV (United States). Dept. of Physics and Astronomy
  4. NASA Goddard Space Flight Center (GSFC), Greenbelt, MD (United States)
  5. Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Ohio Univ., Athens, OH (United States). Astrophysical Inst.
  6. Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Univ. of Nevada, Las Vegas, NV (United States). Dept. of Physics and Astronomy
Publication Date:
Report Number(s):
LA-UR-15-28215
Journal ID: ISSN 2041-8213
Grant/Contract Number:
AC52-06NA25396
Type:
Accepted Manuscript
Journal Name:
The Astrophysical Journal. Letters
Additional Journal Information:
Journal Volume: 818; Journal Issue: 1; Journal ID: ISSN 2041-8213
Publisher:
Institute of Physics (IOP)
Research Org:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS; acceleration of particles; magnetic reconnection; relativistic processes; gamm-ray bursts: general; galaxies: jet; pulsars: general
OSTI Identifier:
1335606