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Title: The Roles of Fluid Compression and Shear in Electron Energization during Magnetic Reconnection

Abstract

Particle acceleration in space and astrophysical reconnection sites is an important unsolved problem in studies of magnetic reconnection. Earlier kinetic simulations have identified several acceleration mechanisms that are associated with particle drift motions. Here, we show that, for sufficiently large systems, the energization processes due to particle drift motions can be described as fluid compression and shear, and that the shear energization is proportional to the pressure anisotropy of energetic particles. By analyzing results from fully kinetic simulations, we show that the compression energization dominates the acceleration of high-energy particles in reconnection with a weak guide field, and the compression and shear effects are comparable when the guide field is 50% of the reconnecting component. Spatial distributions of those energization effects reveal that reconnection exhausts, contracting islands, and island-merging regions are the three most important regions for compression and shear acceleration. This study connects particle energization by particle guiding-center drift motions with that due to background fluid motions, as in the energetic particle transport theory. It provides foundations for building particle transport models for large-scale reconnection acceleration such as those in solar flares.

Authors:
ORCiD logo [1]; ORCiD logo [2]; ORCiD logo [1]; ORCiD logo [3]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  2. Los Alamos National Lab. (LANL), Los Alamos, NM (United States); New Mexico Consortium, Los Alamos, NM (United States)
  3. Space Science Inst., Boulder, CO (United States); Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States); New Mexico Consortium, Los Alamos, NM (United States); Space Science Inst., Boulder, CO (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Fusion Energy Sciences (FES) (SC-24); LANL Laboratory Directed Research and Development (LDRD) Program; National Aeronautic and Space Administration (NASA)
OSTI Identifier:
1463496
Report Number(s):
LA-UR-18-21317
Journal ID: ISSN 1538-4357; TRN: US1902308
Grant/Contract Number:  
AC52-06NA25396; SC0018240; NNH16AC60I
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
The Astrophysical Journal (Online)
Additional Journal Information:
Journal Volume: 855; 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; 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; acceleration of particles; accretion; accretion disks; magnetic reconnection; Sun; corona; flares

Citation Formats

Li, Xiaocan, Guo, Fan, Li, Hui, and Birn, Joachim. The Roles of Fluid Compression and Shear in Electron Energization during Magnetic Reconnection. United States: N. p., 2018. Web. doi:10.3847/1538-4357/aaacd5.
Li, Xiaocan, Guo, Fan, Li, Hui, & Birn, Joachim. The Roles of Fluid Compression and Shear in Electron Energization during Magnetic Reconnection. United States. doi:10.3847/1538-4357/aaacd5.
Li, Xiaocan, Guo, Fan, Li, Hui, and Birn, Joachim. Fri . "The Roles of Fluid Compression and Shear in Electron Energization during Magnetic Reconnection". United States. doi:10.3847/1538-4357/aaacd5. https://www.osti.gov/servlets/purl/1463496.
@article{osti_1463496,
title = {The Roles of Fluid Compression and Shear in Electron Energization during Magnetic Reconnection},
author = {Li, Xiaocan and Guo, Fan and Li, Hui and Birn, Joachim},
abstractNote = {Particle acceleration in space and astrophysical reconnection sites is an important unsolved problem in studies of magnetic reconnection. Earlier kinetic simulations have identified several acceleration mechanisms that are associated with particle drift motions. Here, we show that, for sufficiently large systems, the energization processes due to particle drift motions can be described as fluid compression and shear, and that the shear energization is proportional to the pressure anisotropy of energetic particles. By analyzing results from fully kinetic simulations, we show that the compression energization dominates the acceleration of high-energy particles in reconnection with a weak guide field, and the compression and shear effects are comparable when the guide field is 50% of the reconnecting component. Spatial distributions of those energization effects reveal that reconnection exhausts, contracting islands, and island-merging regions are the three most important regions for compression and shear acceleration. This study connects particle energization by particle guiding-center drift motions with that due to background fluid motions, as in the energetic particle transport theory. It provides foundations for building particle transport models for large-scale reconnection acceleration such as those in solar flares.},
doi = {10.3847/1538-4357/aaacd5},
journal = {The Astrophysical Journal (Online)},
issn = {1538-4357},
number = 2,
volume = 855,
place = {United States},
year = {2018},
month = {3}
}

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Cited by: 9 works
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    • Sitnov, Mikhail; Birn, Joachim; Ferdousi, Banafsheh
    • Space Science Reviews, Vol. 215, Issue 4
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    Explosive Magnetotail Activity
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    • Space Science Reviews, Vol. 215, Issue 4
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