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Title: Phase space structure of the electron diffusion region in reconnection with weak guide fields

Abstract

Kinetic simulations of magnetic reconnection provide detailed information about the electric and magnetic structure throughout the simulation domain, as well as high resolution profiles of the essential fluid parameters including the electron and ion densities, flows, and pressure tensors. However, the electron distribution function, f(v), within the electron diffusion region becomes highly structured in the three dimensional velocity space and is not well resolved by the data available from the particle-in-cell (PIC) simulations. Here, we reconstruct the electron distribution function within the diffusion region at enhanced resolution. This is achieved by tracing electron orbits in the fields taken from PIC simulations back to the inflow region where an analytic form of the magnetized electron distribution is known. For antiparallel reconnection, the analysis reveals the highly structured nature of f(v), with striations corresponding to the number of times electrons have been reflected within the reconnection current layer, and exposes the origin of gradients in the electron pressure tensor important for momentum balance. The structure of the reconnection region is strongly tied to the pressure anisotropy that develops in the electrons upstream of the reconnection region. The addition of a guide field changes the nature of the electron distributions, and the differencesmore » are accounted for by studying the motion of single particles in the field geometry. Finally, the geometry of small guide field reconnection is shown to be highly sensitive to the ion/electron mass ratio applied in the simulation.« less

Authors:
; ;  [1];  [2]
  1. Department of Physics, and Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)
  2. Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)
Publication Date:
OSTI Identifier:
22068873
Resource Type:
Journal Article
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 19; Journal Issue: 11; Other Information: (c) 2012 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 1070-664X
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ANISOTROPY; DIFFUSION; DISTRIBUTION FUNCTIONS; ELECTRON DENSITY; ELECTRONS; GEOMETRY; ION DENSITY; MAGNETIC RECONNECTION; ORBITS; PHASE SPACE; PLASMA SIMULATION; STRIATIONS; THREE-DIMENSIONAL CALCULATIONS

Citation Formats

Ng, J., Egedal, J., Le, A., and Daughton, W. Phase space structure of the electron diffusion region in reconnection with weak guide fields. United States: N. p., 2012. Web. doi:10.1063/1.4766895.
Ng, J., Egedal, J., Le, A., & Daughton, W. Phase space structure of the electron diffusion region in reconnection with weak guide fields. United States. doi:10.1063/1.4766895.
Ng, J., Egedal, J., Le, A., and Daughton, W. Thu . "Phase space structure of the electron diffusion region in reconnection with weak guide fields". United States. doi:10.1063/1.4766895.
@article{osti_22068873,
title = {Phase space structure of the electron diffusion region in reconnection with weak guide fields},
author = {Ng, J. and Egedal, J. and Le, A. and Daughton, W.},
abstractNote = {Kinetic simulations of magnetic reconnection provide detailed information about the electric and magnetic structure throughout the simulation domain, as well as high resolution profiles of the essential fluid parameters including the electron and ion densities, flows, and pressure tensors. However, the electron distribution function, f(v), within the electron diffusion region becomes highly structured in the three dimensional velocity space and is not well resolved by the data available from the particle-in-cell (PIC) simulations. Here, we reconstruct the electron distribution function within the diffusion region at enhanced resolution. This is achieved by tracing electron orbits in the fields taken from PIC simulations back to the inflow region where an analytic form of the magnetized electron distribution is known. For antiparallel reconnection, the analysis reveals the highly structured nature of f(v), with striations corresponding to the number of times electrons have been reflected within the reconnection current layer, and exposes the origin of gradients in the electron pressure tensor important for momentum balance. The structure of the reconnection region is strongly tied to the pressure anisotropy that develops in the electrons upstream of the reconnection region. The addition of a guide field changes the nature of the electron distributions, and the differences are accounted for by studying the motion of single particles in the field geometry. Finally, the geometry of small guide field reconnection is shown to be highly sensitive to the ion/electron mass ratio applied in the simulation.},
doi = {10.1063/1.4766895},
journal = {Physics of Plasmas},
issn = {1070-664X},
number = 11,
volume = 19,
place = {United States},
year = {2012},
month = {11}
}