Octupolar out-of-plane magnetic field structure generation during collisionless magnetic reconnection in a stressed <i>X</i>-point collapse

Pahlen, J. Graf von der; Tsiklauri, David

doi:10.1063/1.4885378

Cited by 5 publications

(13 citation statements)

References 22 publications

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“…Following Graf von der Pahlen & Tsiklauri (2014a), Graf von der Pahlen & Tsiklauri (2014b), and Graf von der Pahlen & Tsiklauri (2015), this study continues the investigation of X-point collapse using a relativistic and fully electromagnetic PIC code. While in previous studies the simulation runs were limited to 2.5D, in this study results were extended into 3D.…”

Section: Pic Simulation Set-upmentioning

confidence: 99%

“…the formation of a current sheet, magnetic Hall field generation, and independence of system size. However, simulations of X-point collapse have also uncovered several new features, such as initial oscillatory reconnection and vortex formation in the high guide-field regime (Graf von der Pahlen & Tsiklauri 2014a) and a distinct octupolar out-of-plane magnetic field (Graf von der Pahlen & Tsiklauri 2014b, which makes this set-up a useful device for the ongoing study of magnetic reconnection. In this study we extend the results of Graf von der Pahlen & Tsiklauri (2014a) where collisionless X-point collapse with a magnetic guide-field was investigated in a 2.5 PIC simulation.…”

Section: Introductionmentioning

confidence: 99%

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Role of electron inertia and reconnection dynamics in a stressedX-point collapse with a guide-field

Pahlen

Tsiklauri

2016

A&A

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Aims. In previous simulations of collisionless 2D magnetic reconnection it was consistently found that the term in the generalised Ohm's law that breaks the frozen-in condition is the divergence of the electron pressure tensor's non-gyrotropic components. The motivation for this study is to investigate the effect of the variation of the guide-field on the reconnection mechanism in simulations of X-point collapse, and the related changes in reconnection dynamics. Methods. A fully relativistic particle-in-cell (PIC) code was used to model X-point collapse with a guide-field in two and three spatial dimensions.Results. We show that in a 2D X-point collapse with a guide-field close to the strength of the in-plane field, the increased induced shear flows along the diffusion region lead to a new reconnection regime in which electron inertial terms play a dominant role at the X-point. This transition is marked by the emergence of a magnetic island -and hence a second reconnection site -as well as electron flow vortices moving along the current sheet. The reconnection electric field at the X-point is shown to exceed all lower guide-field cases for a brief period, indicating a strong burst in reconnection. By extending the simulation to three spatial dimensions it is shown that the locations of vortices along the current sheet (visualised by their Q-value) vary in the out-of-plane direction, producing tilted vortex tubes. The vortex tubes on opposite sides of the diffusion region are tilted in opposite directions, similarly to bifurcated current sheets in oblique tearing-mode reconnection. The tilt angles of vortex tubes were compared to a theoretical estimation and were found to be a good match. Particle velocity distribution functions for different guide-field runs, for 2.5D and 3D simulations, are analysed and compared.

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Section: Pic Simulation Set-upmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Role of electron inertia and reconnection dynamics in a stressedX-point collapse with a guide-field

Pahlen

Tsiklauri

2016

A&A

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“…The out-ofplane magnetic field that emerged in Ref. [16] was shown to have the well-known quadrupolar field at the centre, generated by electron currents, and four regions of opposite magnetic polarity on the outside, resulting from ion currents, as illustrated in Fig. 1.…”

Section: Introductionmentioning

confidence: 99%

“…(Right panel) The setup and resulting current and out-ofplane magnetic field generation for X-point collapse, from simulations in Ref. [16]. It is shown that, as in-plane field lines reconnect, electrons move towards and then away from the X-point, generating quadrupolar structure as described in Ref.…”

Section: Introductionmentioning

confidence: 99%

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The effects of ion mass variation and domain size on octupolar out-of-plane magnetic field generation in collisionless magnetic reconnection

Pahlen

Tsiklauri

2015

Physics of Plasmas

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J. Graf von der Pahlen and D. Tsiklauri, Phys. Plas. 21, 060705 (2014), established that the generation of octupolar out-of-plane magnetic field structure in a stressed X-point collapse is due to ion currents. The field has a central region, comprising of the well-known qaudrupolar field (quadrupolar components), as well as four additional poles of reversed polarity closer to the corners of the domain (octupolar components). In this extended work, the dependence of the octupolar structure on domain size and ion mass variation is investigated. Simulations show that the strength and spatial structure of the generated octupolar magnetic field is independent of ion to electron mass ratio. Thus showing that ion currents play a significant role in out-of-plane magnetic structure generation in physically realistic scenarios. Simulations of different system sizes show that the width of the octupolar structure remains the same and has a spacial extent of the order of the ion inertial length. The width of the structure thus appears to be independent on boundary condition effects. The length of the octupolar structure however increases for greater domain sizes, prescribed by the external system size. This was found to be a consequence of the structure of the in-plane magnetic field in the outflow region halting the particle flow and thus terminating the in-plane currents that generate the out-of-plane field. The generation of octupolar magnetic field structure is also established in a tearing-mode reconnection scenario. The differences in the generation of the octupolar field and resulting qualitative differences between X-point collapse and tearing-mode are discussed.

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Kinetic Alfven wave (KAW) eigenmode in magnetosphere magnetic reconnection

Dai

Wang

2022

Rev. Mod. Plasma Phys.

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One prominent signature of collisionless magnetic reconnection in the magnetosphere is the Hall effect. In the ion-scale region of reconnection, ions cannot follow the magnetic field line whereas electrons are still magnetized. The difference in the motions of electrons and ions leads to charge separation, the resulting transverse Hall electric field, the field-aligned streaming of electrons to preserve charge neutrality, and the corresponding Hall magnetic field. Such physics has long been invoked in the discovery of kinetic Alfven waves (KAW) when the perpendicular wavelength becomes comparable to the ion scale. In this review, we present recent progresses in theoretical modeling, numerical simulations and in situ observations that analyze Hall effects in terms of KAW eigenmode. This review will also cover analysis of the impact of KAW eigenmode on the ion acceleration and energy conversion in reconnection. We emphasize that the KAW perspective can provide a unified description of various phenomena in magnetic reconnection, including Hall magnetic fields, Hall electric fields, the field-aligned current, the electric field parallel to B, the non-gyrotropy velocity distribution of ions, and a close connection between Hall fields and a fast reconnection rate ($$\sim$$ ∼ 0.1). The quantitative description of these aspects is necessary for a Petschek-type model in the era of collisionless reconnection.

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Octupolar out-of-plane magnetic field structure generation during collisionless magnetic reconnection in a stressed X-point collapse

Cited by 5 publications

References 22 publications

Role of electron inertia and reconnection dynamics in a stressedX-point collapse with a guide-field

Role of electron inertia and reconnection dynamics in a stressedX-point collapse with a guide-field

The effects of ion mass variation and domain size on octupolar out-of-plane magnetic field generation in collisionless magnetic reconnection

Kinetic Alfven wave (KAW) eigenmode in magnetosphere magnetic reconnection

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