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Title: Electron acceleration by parallel and perpendicular electric fields during magnetic reconnection without guide field

Abstract

Electron acceleration due to the electric field parallel to the background magnetic field during magnetic reconnection with no guide field is investigated by theory and two-dimensional electromagnetic particle-in-cell simulations and compared with acceleration due to the electric field perpendicular to the magnetic field. The magnitude of the parallel electric potential shows dependence on the ratio of the plasma frequency to the electron cyclotron frequency as (ω pee) -2 and on the background plasma density as N$$^{-½}_{b}$$. In the Earth's magnetotail, the parameter ω pee~9 and the background (lobe) density can be of the order of 0.01 cm -3, and it is expected that the parallel electric potential is not large enough to accelerate electrons up to 100 keV. Therefore, we must consider the effect of the perpendicular electric field to account for electron energization in excess of 100 keV in the Earth's magnetotail. Trajectories for high-energy electrons are traced in a simulation to demonstrate that acceleration due to the perpendicular electric field in the diffusion region is the dominant acceleration mechanism, rather than acceleration due to the parallel electric fields in the exhaust regions. For energetic electrons accelerated near the X line due to the perpendicular electric field, pitch angle scattering converts the perpendicular momentum to the parallel momentum. On the other hand, for passing electrons that are mainly accelerated by the parallel electric field, pitch angle scattering converting the parallel momentum to the perpendicular momentum occurs. In this way, particle acceleration and pitch angle scattering will generate heated electrons in the exhaust regions.

Authors:
 [1];  [1];  [2];  [3]
  1. Department of AstronomyUniversity of Maryland College Park Maryland USA; Heliophysics Science DivisionNASA Goddard Space Flight Center Greenbelt Maryland USA
  2. Space Science CenterUniversity of New Hampshire Durham New Hampshire USA
  3. Center for Heliophysics and Princeton Plasma Physics LaboratoryPrinceton University Princeton New Jersey USA
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Oak Ridge Leadership Computing Facility (OLCF)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1565403
Resource Type:
Journal Article
Journal Name:
Journal of Geophysical Research. Space Physics
Additional Journal Information:
Journal Volume: 120; Journal Issue: 11; Journal ID: ISSN 2169-9380
Publisher:
American Geophysical Union
Country of Publication:
United States
Language:
English
Subject:
Astronomy & Astrophysics

Citation Formats

Bessho, N., Chen, L. ‐J., Germaschewski, K., and Bhattacharjee, A. Electron acceleration by parallel and perpendicular electric fields during magnetic reconnection without guide field. United States: N. p., 2015. Web. doi:10.1002/2015ja021548.
Bessho, N., Chen, L. ‐J., Germaschewski, K., & Bhattacharjee, A. Electron acceleration by parallel and perpendicular electric fields during magnetic reconnection without guide field. United States. doi:10.1002/2015ja021548.
Bessho, N., Chen, L. ‐J., Germaschewski, K., and Bhattacharjee, A. Sun . "Electron acceleration by parallel and perpendicular electric fields during magnetic reconnection without guide field". United States. doi:10.1002/2015ja021548.
@article{osti_1565403,
title = {Electron acceleration by parallel and perpendicular electric fields during magnetic reconnection without guide field},
author = {Bessho, N. and Chen, L. ‐J. and Germaschewski, K. and Bhattacharjee, A.},
abstractNote = {Electron acceleration due to the electric field parallel to the background magnetic field during magnetic reconnection with no guide field is investigated by theory and two-dimensional electromagnetic particle-in-cell simulations and compared with acceleration due to the electric field perpendicular to the magnetic field. The magnitude of the parallel electric potential shows dependence on the ratio of the plasma frequency to the electron cyclotron frequency as (ωpe/Ωe)-2 and on the background plasma density as N$^{-½}_{b}$. In the Earth's magnetotail, the parameter ωpe/Ωe~9 and the background (lobe) density can be of the order of 0.01 cm-3, and it is expected that the parallel electric potential is not large enough to accelerate electrons up to 100 keV. Therefore, we must consider the effect of the perpendicular electric field to account for electron energization in excess of 100 keV in the Earth's magnetotail. Trajectories for high-energy electrons are traced in a simulation to demonstrate that acceleration due to the perpendicular electric field in the diffusion region is the dominant acceleration mechanism, rather than acceleration due to the parallel electric fields in the exhaust regions. For energetic electrons accelerated near the X line due to the perpendicular electric field, pitch angle scattering converts the perpendicular momentum to the parallel momentum. On the other hand, for passing electrons that are mainly accelerated by the parallel electric field, pitch angle scattering converting the parallel momentum to the perpendicular momentum occurs. In this way, particle acceleration and pitch angle scattering will generate heated electrons in the exhaust regions.},
doi = {10.1002/2015ja021548},
journal = {Journal of Geophysical Research. Space Physics},
issn = {2169-9380},
number = 11,
volume = 120,
place = {United States},
year = {2015},
month = {11}
}

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