Aspects of collisionless magnetic reconnection in asymmetric systems

Hesse, Michael; Aunai, N.; Zenitani, Seiji; Кузнецова, М. М.; Birn, J.

doi:10.1063/1.4811467

Cited by 67 publications

(121 citation statements)

References 17 publications

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“…The simulation is designed to provide optimal signal-to-noise ratios for particle distributions (simulations with larger mass ratios and system size produce qualitatively similar results), following successes predicting observed distributions [11,24]. Figure (1) displays an overview of a subdomain of the simulated system around the in-plane null for the time of the peak reconnection rate, which is reached at approximately t=25 [20]. This rate varies slowly, it is within 10% of its peak value for about 16 ion cyclotron times [20].…”

Section: Model and Resultsmentioning

confidence: 99%

“…Figure (1) displays an overview of a subdomain of the simulated system around the in-plane null for the time of the peak reconnection rate, which is reached at approximately t=25 [20]. This rate varies slowly, it is within 10% of its peak value for about 16 ion cyclotron times [20]. Shown from top to bottom are the parallel electric field (E || ), the z-component of the electric field (E z ), the out-of-plane magnetic field (B y ), and the out-of-plane electron current density (j ye ), with in-plane magnetic field (white contours), and electron flow vectors (gold arrows whose lengths represent the flow magnitudes).…”

Section: Model and Resultsmentioning

confidence: 99%

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Population Mixing in Asymmetric Magnetic Reconnection with a Guide Field

et al. 2017

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Section: Model and Resultsmentioning

confidence: 99%

Section: Model and Resultsmentioning

confidence: 99%

Population Mixing in Asymmetric Magnetic Reconnection with a Guide Field

et al. 2017

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“…Large‐scale simulations are performed with the electromagnetic PIC code VPIC (Bowers et al, ). The initial asymmetric CS (Aunai et al, ; Hesse et al, ; Pritchett, ; Liu et al, , ) is given by the magnetic profile

{boldB}_{0} = B_{0} false[false(0.5 + S false) \overset{boldx}{true} + b_{g} \overset{boldy}{true} false]

with

S = \tanh false[false(z - z_{0} false) false/ L false]

, where the guide field strength is

B_{g} false/ B_{0}

b_{g}

and

z_{0}

is the shift of the CS from

z = 0

. This profile gives asymptotic magnetic fields

B_{2 x 0} = 1.5 B_{0}

and

B_{1 x 0} = - 0.5 B_{0}

where the subscripts “1” and “2” correspond to the magnetosheath and magnetosphere sides, respectively.…”

Section: Simulation Setup and Methodsmentioning

confidence: 99%

Three‐Dimensional X‐line Spreading in Asymmetric Magnetic Reconnection

Liu

Hesse

et al. 2020

JGR Space Physics

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Three‐dimensional X‐line spreading is important for the coupling between global dynamics and local kinetic physics of magnetic reconnection. Using large‐scale 3‐D particle‐in‐cell simulations, we investigate the spreading of the X‐line out of the reconnection plane under a strong guide field in asymmetric reconnection. The X‐line spreading speed depends strongly on the equilibrium current sheet thickness. In a simulation with a thick, ion‐scale equilibrium current sheet (CS), the X‐line spreads at the ambient species drift speeds, which are significantly lower than the Alfvén speed based on the guide field VAg(sub‐Alfvénic spreading). In simulations with a sub‐ion‐scale CS, the X‐line spreads at VAg instead (Alfvénic spreading). An Alfvénic signal consistent with kinetic Alfvén waves develops and propagates, leading to CS thinning and extending, which ultimately causes reconnection onset. The continuous onset of reconnection along the propagation direction of the signal manifests as Alfvénic X‐line spreading. The strong dependence on the CS thickness of the spreading speeds and the orientation of the X‐line are consistent with the collisionless tearing instability. Our simulations indicate that when the collisionless tearing growth is sufficiently strong in a thinner CS such that γfalse/normalΩci≳scriptOfalse(1false), Alfvénic X‐line spreading can effectively take place. Our results compare favorably with a number of numerical simulations and recent magnetopause observations. An important implication of this work is that the magnetopause CS is typically too thick for the X‐line to spread at the Alfvén speed.

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“…Magnetic reconnection in magnetized coronae and jets probably often implies asymmetric plasmas from each side of the current sheet, guide fields Hesse et al 2013;Eastwood et al 2013), and also normal fields (alongx here) reminiscent of the ambient magnetic field. The last point has been studied in the context of the Earth magnetotail (Pritchett 2005a(Pritchett , 2010Sitnov & Swisdak 2011).…”

Section: Other Complicationsmentioning

confidence: 99%

Relativistic magnetic reconnection in collisionless ion-electron plasmas explored with particle-in-cell simulations

Melzani

Walder

Folini

et al. 2014

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Magnetic reconnection is a leading mechanism for magnetic energy conversion and high-energy non-thermal particle production in a variety of high-energy astrophysical objects, including ones with relativistic ion-electron plasmas (e.g., microquasars or AGNs), a regime where first principle studies are scarce. We present 2D particle-in-cell (PIC) simulations of low β ion-electron plasmas under relativistic conditions, i.e., with inflow magnetic energy exceeding the plasma restmass energy. We identify outstanding properties: (i) For relativistic inflow magnetizations (here 10 ≤ σ e ≤ 360), the reconnection outflows are dominated by thermal agitation instead of bulk kinetic energy. (ii) At high inflow electron magnetization (σ e ≥ 80), the reconnection electric field is sustained more by bulk inertia than by thermal inertia. It challenges the thermal-inertia paradigm and its implications. (iii) The inflows feature sharp transitions at the entrance of the diffusion zones. These are not shocks but results from particle ballistic motions, all bouncing at the same location, provided that the thermal velocity in the inflow is far lower than the inflow E × B bulk velocity. (iv) Island centers are magnetically isolated from the rest of the flow and can present a density depletion at their center. (v) The reconnection rates are slightly higher than in non-relativistic studies. They are best normalized by the inflow relativistic Alfvén speed projected in the outflow direction, which then leads to rates in a close range (0.14-0.25), thus allowing for an easy estimation of the reconnection electric field.

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Aspects of collisionless magnetic reconnection in asymmetric systems

Cited by 67 publications

References 17 publications

Population Mixing in Asymmetric Magnetic Reconnection with a Guide Field

Population Mixing in Asymmetric Magnetic Reconnection with a Guide Field

Three‐Dimensional X‐line Spreading in Asymmetric Magnetic Reconnection

Relativistic magnetic reconnection in collisionless ion-electron plasmas explored with particle-in-cell simulations

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