Regimes of the Electron Diffusion Region in Magnetic Reconnection

Lê, A.; Egedal, J.; Ohia, O.; Daughton, W.; Karimabadi, H.; Lukin, V. S.

doi:10.1103/physrevlett.110.135004

Cited by 110 publications

(153 citation statements)

References 25 publications

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“…One example is the deflection of electron-jets associated with the socalled external diffusion region seen in strictly anti-parallel simulations with M i /m e ratios as low as 25 ). The critical B g for electron-jet deflection depends on mass ratio as (Le et al 2013) and is consistent with earlier studies using both physical and artificial mass ratios . Hence, as far as electronscale processes are concerned, the assumed guide field B g = 0.1B 0 in simulations described in this paper has the same effect as B g = 0.04B 0 for a physical mass ratio, M i /m e = 1836, and is equivalent to B g = 0.3B 0 in a number of other simulations employing a mass ratio, M i /m e = 25.…”

Section: Physical Picture Of Tail Reconnection From 2-d Simulations Asupporting

confidence: 74%

“…In the majority of measured tail reconnection events characterized as anti-parallel (Eastwood et al 2010a(Eastwood et al , 2010b) a small guide field, B g ≤ 1 nT may still be present (Eastwood, private communication). However simulations show that a guide field of B g ≤ 1 nT can have significant measurable consequences Le et al 2013) which are missing from antiparallel reconnection simulations in which B g is take as strictly zero. In most of the implicit PIC simulations described in this paper the ion to electron mass-ratio is taken to be M i /m e = 256 and the guide field is taken to be B g = 0.1B 0 .…”

Section: Physical Picture Of Tail Reconnection From 2-d Simulations Amentioning

confidence: 99%

“…However significant progress has been made in recent years towards using physical mass ratios in reconnection simulations Le et al 2013).…”

Section: Simulationsmentioning

confidence: 99%

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What Can We Learn about Magnetotail Reconnection from 2D PIC Harris-Sheet Simulations?

2015

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The Magnetosphere Multiscale Mission (MMS) will provide the first opportunity to probe electron-scale physics during magnetic reconnection in Earth's magnetopause and magnetotail. This article will address only tail reconnection-as a non-steady-state process in which the first reconnected field lines advance away from the x-point in flux pile-up fronts directed Earthward and anti-Earthward. An up-to-date microscopic physical picture of electron and ion-scale collisionless tail reconnection processes is presented based on 2-D Particle-In-Cell (PIC) simulations initiated from a Harris current sheet and on Cluster and Themis measurements of tail reconnection. The successes and limitations of simulations when compared to measured reconnection are addressed in detail. The main focus is on particle and field diffusion region signatures in the tail reconnection geometry. The interpretation of these signatures is vital to enable spacecraft to identify physically significant reconnection events, to trigger meaningful data transfer from MMS to Earth and to construct a useful overall physical picture of tail reconnection. New simulation results and theoretical interpretations are presented for energy transport of particles and fields, for the size and shape of electron and ion diffusion regions, for processes occurring near the fronts and for the j × B (Hall) electric field.

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Section: Physical Picture Of Tail Reconnection From 2-d Simulations Asupporting

confidence: 74%

Section: Physical Picture Of Tail Reconnection From 2-d Simulations Amentioning

confidence: 99%

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What Can We Learn about Magnetotail Reconnection from 2D PIC Harris-Sheet Simulations?

2015

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“…The parameters employed in these simulations are appropriate to Earth's magnetotail and identical to those employed in our published simulations [26] and confirmed by others [27]. The electron temperature is T e ¼ 1 keV and T i ¼ 5T e .…”

mentioning

confidence: 97%

Čerenkov Emission of Quasiparallel Whistlers by Fast Electron Phase-Space Holes during Magnetic Reconnection

et al. 2014

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Kinetic simulations of magnetotail reconnection have revealed electromagnetic whistlers originating near the exhaust boundary and propagating into the inflow region. The whistler production mechanism is not a linear instability, but rather is Čerenkov emission of almost parallel whistlers from localized moving clumps of charge (finite-size quasiparticles) associated with nonlinear coherent electron phase space holes. Whistlers are strongly excited by holes without ever growing exponentially. In the simulation the whistlers are emitted in the source region from holes that accelerate down the magnetic separatrix towards the x line. The phase velocity of the whistlers v φ in the source region is everywhere well matched to the hole velocity v H as required by the Čerenkov condition. The simulation shows emission is most efficient near the theoretical maximum v φ ¼ half the electron Alfven speed, consistent with the new theoretical prediction that faster holes radiate more efficiently. While transferring energy to whistlers the holes lose coherence and dissipate over a few local ion inertial lengths. The whistlers, however, propagate to the x line and out over many 10's of ion inertial lengths into the inflow region of reconnection. As the whistlers pass near the x line they modulate the rate at which magnetic field lines reconnect. Electromagnetic (EM) whistler waves are commonly found in space [1][2][3][4], and in laboratory experiments [5] and are often observed during magnetic reconnection [6][7][8][9]. Various kinetic electron distributions have been found which drive whistlers unstable. The most commonly cited unstable distributions are electron temperature anisotropy [10] and electron beams [11,12], although there are other unstable distributions [13]. The quasiparticle Čerenkov emission of EM whistler waves found in the reconnection simulations in this Letter via both simulation and theory is a fundamentally different physical mechanism, in which the whistlers do not exponentiate from noise, as in kinetic instabilities.Quasiparticle Čerenkov emission [14] is an unusual process which can be understood simply in terms of an inhomogenous nonlinear current J 0 , in a spatially uniform background plasma. Let J 0 ðξ ∥ − v 0 t; ξ ⊥ Þ ¼ v 0 ρ 0 ðξ ∥ − v 0 t; ξ ⊥ Þ represent a finite-sized spatial clump of coherent charge density ρ 0 moving at speed v 0 along a background magnetic field B 0 in the spatial direction ξ jj . In its own frame ρ 0 ðξ jj ; ξ ⊥ Þ is assumed here to be the stationary charge density of a moving electron phase space hole, found from Poisson's equation in terms of the trapping potential whose parallel gradient is the bipolar electrostatic field associated with phase space holes. Such holes have been observed as bipolar parallel electrostatic field structures in space physics [15][16][17] for over 12 years. They are often associated with magnetic reconnection in magnetospheric [6,18] and laboratory plasmas [19].The spatial transform of the finite-sized hole current iswhich, for a given k jj , osc...

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“…This observation is consistent with a recent numerical study by Le et al (2009), who showed that the temperature anisotropy develops due to electron trapping in the reconnection inflow. Subsequent simulations (Ohia et al 2012;Le et al 2013) predicted that the pressure anisotropy, approaching the firehose condition (p || − p ⊥ = B 2 /μ 0 ), can drive large-scale elongated electron current layers in the exhaust if the guide field is sufficient to maintain magnetized electrons. Figure 3(i), (j), indeed, shows that the firehose condition (reddotted) was approached near the neutral sheet where the elongated electron current layer is observed to be embedded.…”

Section: Plasma Phenomena As Measured In Three Dimensionsmentioning

confidence: 99%

Multipoint observations of plasma phenomena made in space by Cluster

et al. 2015

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Plasmas are ubiquitous in nature, surround our local geospace environment, and permeate the universe. Plasma phenomena in space give rise to energetic particles, the aurora, solar flares and coronal mass ejections, as well as many energetic phenomena in interstellar space. Although plasmas can be studied in laboratory settings, it is often difficult, if not impossible, to replicate the conditions (density, temperature, magnetic and electric fields, etc.) of space. Single-point space missions too numerous to list have described many properties of near-Earth and heliospheric plasmas as measured both in situ and remotely (see http://www.nasa.gov/missions/#.U1mcVmeweRY for a list of NASA-related missions). However, a full description of our plasma environment requires three-dimensional spatial measurements. Cluster is the first, and until data begin flowing from the Magnetospheric Multiscale Mission (MMS), the only mission designed to describe the three-dimensional spatial structure of plasma phenomena in geospace. In this paper, we concentrate on some of the many plasma phenomena that have been studied using data from Cluster. To date, there have been more than 2000 refereed papers published using Cluster data but in this paper we will, of necessity, refer to only a small fraction of the published work. We have focused on a few basic plasma phenomena, but, for example, have not dealt with most of the vast body of work describing dynamical phenomena in Earth's magnetosphere, including the dynamics of current sheets in Earth's magnetotail and the morphology of the dayside high latitude cusp. Several review articles and special publications are available that describe aspects of that research in detail and interested readers are referred to them (see for example, Escoubet et al.

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Regimes of the Electron Diffusion Region in Magnetic Reconnection

Cited by 110 publications

References 25 publications

What Can We Learn about Magnetotail Reconnection from 2D PIC Harris-Sheet Simulations?

What Can We Learn about Magnetotail Reconnection from 2D PIC Harris-Sheet Simulations?

Čerenkov Emission of Quasiparallel Whistlers by Fast Electron Phase-Space Holes during Magnetic Reconnection

Multipoint observations of plasma phenomena made in space by Cluster

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