Computing the reconnection rate in turbulent kinetic layers by using electron mixing to identify topology

Daughton, W.; Nakamura, Takuma; Karimabadi, H.; Roytershteyn, V.; Loring, Burlen

doi:10.1063/1.4875730

Cited by 117 publications

(178 citation statements)

References 59 publications

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“…Recent 2-D and 3-D kinetic simulations demonstrated that repeated formation of secondary small-scale flux ropes near the X-line and within the reconnection exhausts drastically disturb steady reconnection features (e.g., Daughton et al, 2006;Fujimoto and Sydora, 2012;Lapenta et al, 2015). Furthermore, recent 3-D fully kinetic simulations also demonstrated that when considering the strong guide field component, similar turbulent features easily spread even outside these regions and fill the whole reconnection layer through the copious formation of oblique secondary flux ropes (Daughton et al, 2011(Daughton et al, , 2014. Spacecraft observations using Cluster indeed indicated the existence of turbulence near the X-line in the magnetotail (Eastwood et al, 2009).…”

Section: Summary and Discussionmentioning

confidence: 99%

Spatial dimensions of the electron diffusion region in anti-parallel magnetic reconnection

Nakamura

Haseagwa

2016

Ann. Geophys.

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Abstract. Spatial dimensions of the detailed structures of the electron diffusion region in anti-parallel magnetic reconnection were analyzed based on two-dimensional fully kinetic particle-in-cell simulations. The electron diffusion region in this study is defined as the region where the positive reconnection electric field is sustained by the electron inertial and non-gyrotropic pressure components. Past kinetic studies demonstrated that the dimensions of the whole electron diffusion region and the inner non-gyrotropic region are scaled by the electron inertial length d e and the width of the electron meandering motion, respectively. In this study, we successfully obtained more precise scalings of the dimensions of these two regions than the previous studies by performing simulations with sufficiently small grid spacing (1/16-1/8 d e ) and a sufficient number of particles (800 particles cell −1 on average) under different conditions changing the ion-to-electron mass ratio, the background density and the electron β e (temperature). The obtained scalings are adequately supported by some theories considering spatial variations of field and plasma parameters within the diffusion region. In the reconnection inflow direction, the dimensions of both regions are proportional to d e based on the background density. Both dimensions also depend on β e based on the background values, but the dependence in the inner region (∼ 0.375th power) is larger than the whole region (0.125th power) reflecting the orbits of meandering and accelerated electrons within the inner region. In the outflow direction, almost only the non-gyrotropic component sustains the positive reconnection electric field. The dimension of this single-scale diffusion region is proportional to the ionelectron hybrid inertial length (d i d e ) 1/2 based on the background density and weakly depends on the background β e with the 0.25th power. These firm scalings allow us to predict observable dimensions in real space which are indeed in reasonable agreement with past in situ spacecraft observations in the Earth's magnetotail and have important implications for future observations with higher resolutions such as the NASA Magnetospheric Multiscale (MMS) mission.

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Section: Summary and Discussionmentioning

confidence: 99%

Spatial dimensions of the electron diffusion region in anti-parallel magnetic reconnection

Nakamura

Haseagwa

2016

Ann. Geophys.

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“…(d) 3D simulations, despite exhibiting great differences in the structure of the reconnec-tion layer, give reconnection rates similar to those of 2D simulations (e.g., Daughton et al 2014;Guo et al 2015).…”

Section: Thoughts On the Interpretation Of This Problemmentioning

confidence: 99%

“…(e) Simulations in turbulent scenarios lead to current sheets characterized by the same reconnection rate as in the standard laminar picture (e.g., Wendel et al 2013;Daughton et al 2014).…”

Section: Thoughts On the Interpretation Of This Problemmentioning

confidence: 99%

On the value of the reconnection rate

Comisso

Bhattacharjee

2016

J. Plasma Phys.

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Numerical simulations have consistently shown that the reconnection rate in certain collisionless regimes can be fast, on the order of 0.1v A B u , where v A and B u are the Alfvén speed and the reconnecting magnetic field upstream of the ion diffusion region. This particular value has been reported in myriad numerical simulations under disparate conditions. However, despite decades of research, the reasons underpinning this specific value remain mysterious. Here, we present an overview of this problem and discuss the conditions under which the "0.1 value" is attained. Furthermore, we explain why this problem should be interpreted in terms of the ion diffusion region length.

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“…Diffusion regions in two-dimensional reconnection simulations are easier to interpret than in 3D simulations because a boundary surface between unreconnected and reconnected field lines, the magnetic separatrix, exists in 2D reconnection. This paper is limited to interpretations of magnetic reconnection found in 2D PIC simulations although there have been recent simulations of 3D reconnectionboth symmetric (i.e., magnetotail) and asymmetric (i.e., dayside) (Daughton et al 2014). Common theoretical measures of diffusion regions include the following: (i) Slippage.…”

Section: Measures Of Diffusion Regionsmentioning

confidence: 99%

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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Computing the reconnection rate in turbulent kinetic layers by using electron mixing to identify topology

Cited by 117 publications

References 59 publications

Spatial dimensions of the electron diffusion region in anti-parallel magnetic reconnection

Spatial dimensions of the electron diffusion region in anti-parallel magnetic reconnection

On the value of the reconnection rate

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

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