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Title: Energetic electron acceleration during multi-island coalescence

Abstract

The mechanisms for the production of relativistic electrons associated with the coalescence/reconnection of multiple magnetic islands are investigated using two-dimensional particle-in-cell simulations for the case where the initial island half width L is comparable to the ion inertia length. Configurations without and with a uniform magnetic guide field are considered. Significant energization occurs only when the number of islands is reduced to 2 or 3 with wavelength satisfying k{sub x}L(less-or-similar sign)0.2. The energization proceeds in two distinct stages. In the first stage, a small number of electrons are accelerated to relativistic energies at the X-line by the inductive electric field, corresponding to perpendicular acceleration in the absence of the guide field and parallel/anti-parallel acceleration with a guide field. The second stage is associated with the final coalescence into one large island and produces a considerably larger number of relativistic electrons. With a guide field, this stage is dominated by the formation of elongated density cavities along one pair of separatrices and continued direct acceleration at the X-line. Without the guide field, the direct X-line acceleration becomes unimportant, and the acceleration is localized in the flux pile-up regions and results from the curvature drift interacting with the localized inductive electric field.more » Typically, some 15%-20% of the decrease in magnetic field energy is transferred to the electrons, with a few percent appearing in relativistic (E/m{sub e}c{sup 2}>0.3) electrons.« less

Authors:
 [1]
  1. Department of Physics and Astronomy, University of California, Los Angeles, Los Angeles, California 90095-1547 (United States)
Publication Date:
OSTI Identifier:
21254517
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 15; Journal Issue: 10; Other Information: DOI: 10.1063/1.2996321; (c) 2008 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ACCELERATION; COALESCENCE; ELECTRON BEAMS; MAGNETIC ISLANDS; MAGNETIC RECONNECTION; MAGNETOHYDRODYNAMICS; PLASMA SIMULATION; RELATIVISTIC RANGE; TAIL ELECTRONS

Citation Formats

Pritchett, P. L. Energetic electron acceleration during multi-island coalescence. United States: N. p., 2008. Web. doi:10.1063/1.2996321.
Pritchett, P. L. Energetic electron acceleration during multi-island coalescence. United States. doi:10.1063/1.2996321.
Pritchett, P. L. Wed . "Energetic electron acceleration during multi-island coalescence". United States. doi:10.1063/1.2996321.
@article{osti_21254517,
title = {Energetic electron acceleration during multi-island coalescence},
author = {Pritchett, P. L.},
abstractNote = {The mechanisms for the production of relativistic electrons associated with the coalescence/reconnection of multiple magnetic islands are investigated using two-dimensional particle-in-cell simulations for the case where the initial island half width L is comparable to the ion inertia length. Configurations without and with a uniform magnetic guide field are considered. Significant energization occurs only when the number of islands is reduced to 2 or 3 with wavelength satisfying k{sub x}L(less-or-similar sign)0.2. The energization proceeds in two distinct stages. In the first stage, a small number of electrons are accelerated to relativistic energies at the X-line by the inductive electric field, corresponding to perpendicular acceleration in the absence of the guide field and parallel/anti-parallel acceleration with a guide field. The second stage is associated with the final coalescence into one large island and produces a considerably larger number of relativistic electrons. With a guide field, this stage is dominated by the formation of elongated density cavities along one pair of separatrices and continued direct acceleration at the X-line. Without the guide field, the direct X-line acceleration becomes unimportant, and the acceleration is localized in the flux pile-up regions and results from the curvature drift interacting with the localized inductive electric field. Typically, some 15%-20% of the decrease in magnetic field energy is transferred to the electrons, with a few percent appearing in relativistic (E/m{sub e}c{sup 2}>0.3) electrons.},
doi = {10.1063/1.2996321},
journal = {Physics of Plasmas},
number = 10,
volume = 15,
place = {United States},
year = {Wed Oct 15 00:00:00 EDT 2008},
month = {Wed Oct 15 00:00:00 EDT 2008}
}