3D Solar Null Point Reconnection MHD Simulations

Baumann, G.; Galsgaard, K.; Nordlund, Åke

doi:10.1007/s11207-012-0168-5

Cited by 33 publications

(36 citation statements)

References 25 publications

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“…(14) & (15) in Ref. 25 using parameters ν1 = 0.007, ν2 = 0.007 and ν3 = 0.4, the resistivity is η ≈ 10 −3 for both the adiabatic and isothermal cases with the setup described below. This initial resistivity will adjust during the instability growth and deviate from an approximate constant.…”

Section: Mhd Stagger Codementioning

confidence: 99%

Nonlinear evolution of the magnetized Kelvin-Helmholtz instability: From fluid to kinetic modeling

et al. 2013

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The nonlinear evolution of collisionless plasmas is typically a multi-scale process where the energy is injected at large, fluid scales and dissipated at small, kinetic scales. Accurately modelling the global evolution requires to take into account the main micro-scale physical processes of interest. This is why comparison of different plasma models is today an imperative task aiming at understanding cross-scale processes in plasmas. We report here the first comparative study of the evolution of a magnetized shear flow, through a variety of different plasma models by using magnetohydrodynamic, Hall-MHD, two-fluid, hybrid kinetic and full kinetic codes. Kinetic relaxation effects are discussed to emphasize the need for kinetic equilibriums to study the dynamics of collisionless plasmas in non trivial configurations. Discrepancies between models are studied both in the linear and in the nonlinear regime of the magnetized Kelvin-Helmholtz instability, to highlight the effects of small scale processes on the nonlinear evolution of collisionless plasmas. We illustrate how the evolution of a magnetized shear flow depends on the relative orientation of the fluid vorticity with respect to the magnetic field direction during the linear evolution when kinetic effects are taken into account. Even if we found that small scale processes differ between the different models, we show that the feedback from small, kinetic scales to large, fluid scales is negligable in the nonlinear regime. This study show that the kinetic modeling validates the use of a fluid approach at large scales, which encourages the development and use of fluid codes to study the nonlinear evolution of magnetized fluid flows, even in the colisionless regime.

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Section: Mhd Stagger Codementioning

confidence: 99%

Nonlinear evolution of the magnetized Kelvin-Helmholtz instability: From fluid to kinetic modeling

et al. 2013

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“…The Copenhagen stagger code [21][22][23] represents a high order finite difference code, a variant of which was involved with the mentioned Newton challenge. For this work, we use a uniform grid resolution.…”

Section: Finite Difference Runs With the Copenhagen Stagger Codementioning

confidence: 99%

Resistive magnetohydrodynamic reconnection: Resolving long-term, chaotic dynamics

et al. 2013

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In this paper, we address the long-term evolution of an idealised double current system entering reconnection regimes where chaotic behavior plays a prominent role. Our aim is to quantify the energetics in high magnetic Reynolds number evolutions, enriched by secondary tearing events, multiple magnetic island coalescence, and compressive versus resistive heating scenarios. Our study will pay particular attention to the required numerical resolutions achievable by modern (grid-adaptive) computations, and comment on the challenge associated with resolving chaotic island formation and interaction. We will use shock-capturing, conservative, grid-adaptive simulations for investigating trends dominated by both physical (resistivity) and numerical (resolution) parameters, and confront them with (visco-)resistive magnetohydrodynamic simulations performed with very different, but equally widely used discretization schemes. This will allow us to comment on the obtained evolutions in a manner irrespective of the adopted discretization strategy. Our findings demonstrate that all schemes used (finite volume based shock-capturing, high order finite differences, and particle in cell-like methods) qualitatively agree on the various evolutionary stages, and that resistivity values of order 0.001 already can lead to chaotic island appearance. However, none of the methods exploited demonstrates convergence in the strong sense in these chaotic regimes. At the same time, nonperturbed tests for showing convergence over long time scales in ideal to resistive regimes are provided as well, where all methods are shown to agree. Both the advantages and disadvantages of specific discretizations as applied to this challenging problem are discussed.

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“…Such funneling leading to asymmetric outflow jets is also a feature of 2D simulations 44,45 where the outflow on one side is blocked, although the geometry is rather different. More direct comparisons can be made with the similar 3D situation of inclined solar coronal jets containing 3D nulls [46][47][48] where the outflow toward the photosphere is slowed by the pileup of flux beneath the domed fan plane. In light of our results, it suggests that the current sheet near the null must be asymmetric to accommodate the observed asymmetric jetting flows in the vicinity of the null.…”

Section: Discussionmentioning

confidence: 99%

Reconnection at three dimensional magnetic null points: Effect of current sheet asymmetry

Wyper

Jain

2013

Physics of Plasmas

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Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. Asymmetric current sheets are likely to be prevalent in both astrophysical and laboratory plasmas with complex three dimensional (3D) magnetic topologies. This work presents kinematic analytical models for spine and fan reconnection at a radially symmetric 3D null (i.e., a null where the eigenvalues associated with the fan plane are equal) with asymmetric current sheets. Asymmetric fan reconnection is characterized by an asymmetric reconnection of flux past each spine line and a bulk flow of plasma across the null point. In contrast, asymmetric spine reconnection is characterized by the reconnection of an equal quantity of flux across the fan plane in both directions. The higher modes of spine reconnection also include localized wedges of vortical flux transport in each half of the fan. In this situation, two definitions for reconnection rate become appropriate: a local reconnection rate quantifying how much flux is genuinely reconnected across the fan plane and a global rate associated with the net flux driven across each semi-plane. Through a scaling analysis, it is shown that when the ohmic dissipation in the layer is assumed to be constant, the increase in the local rate bleeds from the global rate as the sheet deformation is increased. Both models suggest that asymmetry in the current sheet dimensions will have a profound effect on the reconnection rate and manner of flux transport in reconnection involving 3D nulls. V C 2013 AIP Publishing LLC.[http://dx

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3D Solar Null Point Reconnection MHD Simulations

Cited by 33 publications

References 25 publications

Nonlinear evolution of the magnetized Kelvin-Helmholtz instability: From fluid to kinetic modeling

Nonlinear evolution of the magnetized Kelvin-Helmholtz instability: From fluid to kinetic modeling

Resistive magnetohydrodynamic reconnection: Resolving long-term, chaotic dynamics

Reconnection at three dimensional magnetic null points: Effect of current sheet asymmetry

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