Anomalous resistivity due to kink modes in a thin current sheet

Moritaka, Toseo; Horiuchi, Ritoku; Ohtani, Hiroaki

doi:10.1063/1.2767623

Cited by 17 publications

(18 citation statements)

References 48 publications

(54 reference statements)

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“…In analyzing the instability development at the front, it is important to separate out the average and the wavy parts of plasma variables. In what follows, we denote a quantity a averaged in the z direction as 〈 a 〉 z , and the perturbed values are

ã = a - {〈 a 〉}_{z}

, leading to

{〈 ã 〉}_{z} = 0

[see, e.g., Innocenti and Lapenta , ; Moritaka et al ., ]. The front position x F is defined as a point at the line y = L y /2, where the value of 〈 n e ( x , L y /2, z )〉 z peaks.…”

Section: Three‐dimensional Simulationsmentioning

confidence: 99%

Evolution of the lower hybrid drift instability at reconnection jet front

et al. 2015

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We investigate current‐driven modes developing at jet fronts during collisionless reconnection. Initial evolution of the reconnection is simulated using conventional 2‐D setup starting from the Harris equilibrium. Three‐dimensional PIC calculations are implemented at later stages, when fronts are fully formed. Intense currents and enhanced wave activity are generated at the fronts because of the interaction of the fast flow plasma and denser ambient current sheet plasma. The study reveals that the lower hybrid drift instability develops quickly in the 3‐D simulation. The instability produces strong localized perpendicular electric fields, which are several times larger than the convective electric field at the front, in agreement with Time History of Events and Macroscale Interactions during Substorms observations. The instability generates waves, which escape the front edge and propagate into the undisturbed plasma ahead of the front. The parallel electron pressure is substantially larger in the 3‐D simulation compared to that of the 2‐D. In a time ∼normalΩci−1, the instability forms a layer, which contains a mixture of the jet plasma and current sheet plasma. The results confirm that the lower hybrid drift instability is important for the front evolution and electron energization.

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ã = a - {〈 a 〉}_{z}

, leading to

{〈 ã 〉}_{z} = 0

[see, e.g., Innocenti and Lapenta , ; Moritaka et al ., ]. The front position x F is defined as a point at the line y = L y /2, where the value of 〈 n e ( x , L y /2, z )〉 z peaks.…”

Section: Three‐dimensional Simulationsmentioning

confidence: 99%

Evolution of the lower hybrid drift instability at reconnection jet front

et al. 2015

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“…For complete understanding of collisionless reconnection, another important subject to be investigated is the role of anomalous resistivity associated with plasma instabilities in the presence of a strong guide field. Previous numerical simulation studies in the case of no guide field [4,7,8,20] have demonstrated that anomalous resistivity is generated through the excitation of a drift kink instability [3] in the ion-scale current sheet after nonlinear modification of the current sheet by a lower hybrid drift instability [2]. However, it is easily expected that the anomalous resistivity associated with plasma instabilities is largely altered by a strong guide field.…”

Section: Discussionmentioning

confidence: 90%

“…A series of particle-in-cell (PIC) simulation studies has disclosed that that there are two microscopic mechanisms, which break a frozen-in condition and excite magnetic reconnection in a collisionless plasma without any guide field: one is due to anomalous resistivity associated with plasma instabilities [2][3][4][5][6][7][8] and the other is due to the effect of a nongyrotropic particle motion, called "meandering motion", in the vicinity of a reconnection point [9][10][11][12][13].…”

Section: Introductionmentioning

confidence: 99%

Influence of a Guide Field on Collisionless Driven Reconnection

Horiuchi

Usami

Ohtani

2014

Plasma and Fusion Research

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The influence of a guide field on collisionless driven reconnection is investigated by means of twodimensional electromagnetic particle simulation in an open system. In a quasi-steady state when reconnection electric field evolves fully, a current layer evolves locally in a narrow kinetic region and its scale decreases in proportion to an electron meandering scale as the guide field is intensified. Here, the meandering scale stands for an average spatial scale of nongyrotropic motions in the vicinity of the reconnection point. Force terms associated with off-diagonal components of electron and ion pressure tensors, which are originating from nongyrotropic motions of charged particles, becomes dominant at the reconnection point and sustain the reconnection electric field even when the guide field is strong. It is also found that thermalization of both ions and electrons is suppressed by the guide field. For the weak guide field, an electron nonthermal component is significantly created through a fast outburst from the kinetic region, while for the strong guide field, an ion nonthermal component is generated through the acceleration by an in-plane electric field near the magnetic separatrix.

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“…Particle simulations under various limited conditions have been carried out in three dimensions to study the stability of a Harris current sheet (Horiuchi and Sato, 1999;Lapenta and Brackbill, 2002;Daughton, 2003;Scholer et al, 2003;Ricci et al, 2004;Daughton et al, 2004;Ricci et al, 2005;Silin et al, 2005;Moritaka et al, 2007). It was found that at first the electrostatic LHDI like instabilities at kλ e ∼ 1 are active only at the low-β edge.…”

Section: Mechanisms For Anomalous Resistivitymentioning

confidence: 99%

“…These modifications to the background state lead to secondary electromagnetic instabilities localized at the center of the current sheet. These instabilities are identified as drift kink instabilities (Horiuchi and Sato, 1999;Moritaka et al, 2007), KelvinHelmholtz instabilities (Lapenta and Brackbill, 2002), or collisionless tearing modes Daughton et al, 2004). Combinations of these instabilities are considered to cause substantial increases in the reconnection rate.…”

Section: Mechanisms For Anomalous Resistivitymentioning

confidence: 99%

Magnetic Reconnection

Yamada¹

2009

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We review the fundamental physics of magnetic reconnection in laboratory and space plasmas, by discussing results from theory, numerical simulations, observations from space satellites, and the recent results from laboratory plasma experiments. After a brief review of the well-known early work, we discuss representative recent experimental and theoretical work and attempt to interpret the essence of significant modern findings. In the area of local reconnection physics, many significant findings have been made with regard to two-fluid physics and are related to the cause of fast reconnection. Profiles of the neutral sheet, Hall currents, and the effects of guide field, collisions, and micro-turbulence are discussed to understand the fundamental processes in a local reconnection layer both in space and laboratory plasmas. While the understanding of the global reconnection dynamics is less developed, notable findings have been made on this issue through detailed documentation of magnetic self-organization phenomena in fusion plasmas. Application of magnetic reconnection physics to astrophysical plasmas is also briefly discussed.

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Anomalous resistivity due to kink modes in a thin current sheet

Cited by 17 publications

References 48 publications

Evolution of the lower hybrid drift instability at reconnection jet front

Evolution of the lower hybrid drift instability at reconnection jet front

Influence of a Guide Field on Collisionless Driven Reconnection

Magnetic Reconnection

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