scholarly journals Comparisons of electron acceleration efficiency among different structures during magnetic reconnection: a Cluster multicase study

2015 ◽  
Vol 33 (12) ◽  
pp. 1469-1478 ◽  
Author(s):  
M. Zhou ◽  
T. Li ◽  
X. Deng ◽  
S. Huang ◽  
H. Li
Keyword(s):  
Magnetic Reconnection ◽  
Current Sheet ◽  
Flux Ratio ◽  
Electron Acceleration ◽  
Maximum Efficiency ◽  
Magnetic Island ◽  
Specific Sequence ◽  
Energetic Electrons ◽  
Thin Current Sheet ◽  
Magnetotail Reconnection

Abstract. Magnetic reconnection has long been believed to be an efficient engine for energetic electrons production. Four different structures have been proposed for electrons being energized: flux pileup region, density cavity located around the separatrix, magnetic island and thin current sheet. In this paper, we compare the electron acceleration efficiency among these structures based on 12 magnetotail reconnection events observed by the Cluster spacecraft in 2001–2006. We used the flux ratio between the energetic electrons (> 50 keV) and lower energy electrons (< 26 keV) to quantify the electron acceleration efficiency. We do not find any specific sequence in which electrons are accelerated within these structures, though the flux pileup region, magnetic island and thin current sheet have higher probabilities to reach the maximum efficiency among the four structures than the density cavity. However, the most efficient electron energization usually occurs outside these structures. We suggest that other structures may also play important roles in energizing electrons. Our results could provide important constraints for the further modeling of electron acceleration during magnetic reconnection.

Multispacecraft observations of the electron current sheet, neighboring magnetic islands, and electron acceleration during magnetotail reconnection

2009 ◽  
Vol 16 (5) ◽  
pp. 056501 ◽  
Author(s):  
Li-Jen Chen ◽  
Naoki Bessho ◽  
Bertrand Lefebvre ◽  
Hans Vaith ◽  
Arne Asnes ◽  
...  
Keyword(s):  
Current Sheet ◽  
Electron Acceleration ◽  
Electron Current ◽  
Magnetic Islands ◽  
Magnetotail Reconnection

scholarly journals Effects on magnetic reconnection of a density asymmetry across the current sheet

2008 ◽  
Vol 26 (8) ◽  
pp. 2471-2483 ◽  
Author(s):  
K. G. Tanaka ◽  
A. Retinò ◽  
Y. Asano ◽  
M. Fujimoto ◽  
I. Shinohara ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Electric Field ◽  
Magnetic Reconnection ◽  
Current Sheet ◽  
Three Dimensional ◽  
Flow Region ◽  
Electron Acceleration ◽  
Particle In Cell ◽  
Line Structure ◽  
Simulation Results

Abstract. The magnetopause (MP) reconnection is characterized by a density asymmetry across the current sheet. The asymmetry is expected to produce characteristic features in the reconnection layer. Here we present a comparison between the Cluster MP crossing reported by Retinò et al. (2006) and virtual observations in two-dimensional particle-in-cell simulation results. The simulation, which includes the density asymmetry but has zero guide field in the initial condition, has reproduced well the observed features as follows: (1) The prominent density dip region is detected at the separatrix region (SR) on the magnetospheric (MSP) side of the MP. (2) The intense electric field normal to the MP is pointing to the center of the MP at the location where the density dip is detected. (3) The ion bulk outflow due to the magnetic reconnection is seen to be biased towards the MSP side. (4) The out-of-plane magnetic field (the Hall magnetic field) has bipolar rather than quadrupolar structure, the latter of which is seen for a density symmetric case. The simulation also showed rich electron dynamics (formation of field-aligned beams) in the proximity of the separatrices, which was not fully resolved in the observations. Stepping beyond the simulation-observation comparison, we have also analyzed the electron acceleration and the field line structure in the simulation results. It is found that the bipolar Hall magnetic field structure is produced by the substantial drift of the reconnected field lines at the MSP SR due to the enhanced normal electric field. The field-aligned electrons at the same MSP SR are identified as the gun smokes of the electron acceleration in the close proximity of the X-line. We have also analyzed the X-line structure obtained in the simulation to find that the density asymmetry leads to a steep density gradient in the in-flow region, which may lead to a non-stationary behavior of the X-line when three-dimensional freedom is taken into account.

scholarly journals Energetic electrons generated during solar flares

2015 ◽  
Vol 81 (6) ◽  
Author(s):  
Gottfried Mann
Keyword(s):  
Magnetic Reconnection ◽  
Solar Flares ◽  
Heavy Ions ◽  
Local Heating ◽  
Electron Acceleration ◽  
Energetic Particles ◽  
Particle Accelerator ◽  
Field Energy ◽  
The Sun ◽  
Energetic Electrons

The Sun is a giant particle accelerator. During solar flares, magnetic field energy stored in the corona is suddenly released and transferred to local heating of the coronal plasma, mass motions (e.g. jets) and the generation of energetic particles, i.e. electrons, protons and heavy ions. Basically, a flare occurs as a local enhancement of the emission of electromagnetic radiation from the radio up to the ${\it\gamma}$-ray range on the Sun. That indicates the production of energetic electrons during flares. NASA’s RHESSI mission has the aim to investigate electron acceleration processes by studying the Sun’s X-ray and ${\it\gamma}$-ray emission with high spatial, temporal and spectral resolution, i.e. by means of imaging spectroscopy. A substantial part of the energy released during a flare is carried by these energetic electrons. Apart from them, solar energetic particles, i.e. protons and heavy ions, and coronal mass ejections play an important role in the energy budget of a flare. Here, we focus on electron acceleration. The way in which $10^{36}$ electrons are accelerated up to energies beyond 30 keV is one of the open questions in solar physics. A flare is considered as the manifestation of magnetic reconnection in the solar corona. Which mechanisms lead to the production of energetic electrons in the magnetic reconnection region is discussed in this paper. Two of them are described in more detail.

Cluster observations of energetic electrons and electromagnetic fields within a reconnecting thin current sheet in the Earth's magnetotail

2008 ◽  
Vol 113 (A12) ◽  
pp. n/a-n/a ◽  
Author(s):  
A. Retinò ◽  
R. Nakamura ◽  
A. Vaivads ◽  
Y. Khotyaintsev ◽  
T. Hayakawa ◽  
...  
Keyword(s):  
Current Sheet ◽  
Electromagnetic Fields ◽  
Energetic Electrons ◽  
Thin Current Sheet

scholarly journals Evidence of an extended electron current sheet and its neighboring magnetic island during magnetotail reconnection

2008 ◽  
Vol 113 (A12) ◽  
pp. n/a-n/a ◽  
Author(s):  
L.-J. Chen ◽  
N. Bessho ◽  
B. Lefebvre ◽  
H. Vaith ◽  
A. Fazakerley ◽  
...  
Keyword(s):  
Current Sheet ◽  
Electron Current ◽  
Magnetic Island ◽  
Magnetotail Reconnection

scholarly journals Electron Acceleration by Strong DC Electric Fields in Extragalactic Jets

2000 ◽  
Vol 195 ◽  
pp. 311-312
Author(s):  
Y. E. Litvinenko
Keyword(s):  
Magnetic Field ◽  
Electric Field ◽  
Magnetic Reconnection ◽  
Current Sheet ◽  
Electric Fields ◽  
Electron Acceleration ◽  
Acceleration Time ◽  
Extragalactic Jets ◽  
Dc Electric Field ◽  
The Magnetic Field

Fast magnetic reconnection in extragalactic jets leads to electron acceleration by the DC electric field in the reconnecting current sheet. The maximum electron energy (γ > 106) and the acceleration time (< 106 s) are determined by the magnetic field dynamics in the sheet.

Energetic electron generation by magnetic reconnection in laboratory laser-plasma interactions

2012 ◽  
Vol 78 (4) ◽  
pp. 497-500 ◽  
Author(s):  
Q.-L. DONG ◽  
D.-W. YUAN ◽  
S.-J. WANG ◽  
Y. T. LI ◽  
X. LIU ◽  
...  
Keyword(s):  
Laser Pulse ◽  
Magnetic Reconnection ◽  
Current Sheet ◽  
Laser Plasma ◽  
Energetic Electron ◽  
Energetic Electrons ◽  
Accelerated Electrons ◽  
Laser Plasma Interactions ◽  
Plasma Bubbles ◽  
Electron Generation

AbstractThe magnetic reconnection (MR) configuration was constructed by using two approaching laser-produced plasma bubbles. The characteristics of the MR current sheet were investigated. The driving energy of the laser pulse affects the type of the current sheet. The experiments present “Y-type” and “X-type” current sheets for larger and smaller driving energy, respectively. The energetic electrons were found to be well-collimated. The formation and ejection of plasmoid from the “Y-type” current sheet was expected to enhance the number of accelerated electrons.

scholarly journals Energetic particles in magnetotail reconnection

2014 ◽  
Vol 81 (2) ◽  
Author(s):  
Ivy Bo Peng ◽  
Juris Vencels ◽  
Giovanni Lapenta ◽  
Andrey Divin ◽  
Andris Vaivads ◽  
...  
Keyword(s):  
Magnetic Reconnection ◽  
Energetic Particles ◽  
Lower Hybrid ◽  
Electron Trajectory ◽  
Strong Electron ◽  
Energetic Electrons ◽  
Particle In Cell ◽  
Reconnection Region ◽  
Magnetotail Reconnection ◽  
Drift Instability

We carried out a 3D fully kinetic simulation of Earth's magnetotail magnetic reconnection to study the dynamics of energetic particles. We developed and implemented a new relativistic particle mover in iPIC3D, an implicit Particle-in-Cell code, to correctly model the dynamics of energetic particles. Before the onset of magnetic reconnection, energetic electrons are found localized close to current sheet and accelerated by lower hybrid drift instability. During magnetic reconnection, energetic particles are found in the reconnection region along thex-line and in the separatrices region. The energetic electrons are first present in localized stripes of the separatrices and finally cover all the separatrix surfaces. Along the separatrices, regions with strong electron deceleration are found. In the reconnection region, two categories of electron trajectory are identified. First, part of the electrons are trapped in the reconnection region, bouncing a few times between the outflow jets. Second, part of the electrons pass the reconnection region without being trapped. Different from electrons, energetic ions are localized on the reconnection fronts of the outflow jets.

scholarly journals Electrodynamics in a very thin current sheet leading to magnetic reconnection

2006 ◽  
Vol 13 (5) ◽  
pp. 509-523 ◽  
Author(s):  
N. Singh ◽  
C. Deverapalli ◽  
G. Khazanov
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Electron Temperature ◽  
Magnetic Reconnection ◽  
Current Sheet ◽  
Electron Mass ◽  
Angle Distribution ◽  
Current Disruption ◽  
Thin Current Sheet ◽  
The Magnetic Field

Abstract. We study the formation of a very thin current sheet (CS) and associated plasma electrodynamics using three-dimensional (3-D) particle-in-cell simulations with ion to electron mass ratio M/m=1836. The CS is driven by imposed anti-parallel magnetic fields. The noteworthy features of the temporal evolution of the CS are the following: (i) Steepening of the magnetic field profile Bx(z) in the central part of the CS, (ii) Generation of three-peak current distribution with the largest peak in the CS center as Bx(z) steepens, (iii) Generation of converging electric fields forming a potential well in the CS center in which ions are accelerated. (iv) Electron and ion heating in the central part of the CS by current-driven instabilities (CDI). (v) Re-broadening of the CS due to increased kinetic plasma pressure in the CS center. (vi) Generation of electron temperature anisotropy with temperature perpendicular to the magnetic field being larger than the parallel one. (vii) Current disruption by electron trapping in an explosively growing electrostatic instability (EGEI) and electron tearing instability (ETI). (viii)The onset of EGEI coincides with an increase in the electron temperature above the temperature of the initially hot ions as well as the appearance of new shear in the electron drift velocity. (ix) Bifurcation of the central CS by the current disruption. (x) Magnetic reconnection (MR) beginning near the null in Bx and spreading outward. (xi) Generation of highly energized electrons reaching relativistic speeds and having isotropic pitch-angle distribution in the region of reconnected magnetic fields. We compare some of these features of the current sheet with results from laboratory and space experiments.

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