Magnetic reconnection driven by current repulsion

Richard, R. L.; Sydora, R. D.; Ashour‐Abdalla, M.

doi:10.1063/1.859338

Cited by 23 publications

(69 citation statements)

References 9 publications

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“…Note that the original work by Richard et al (1990) typically employs a force-free magnetic field using a spatially varying vertical magnetic field component with a uniform plasma pressure, although runs with pressure gradient variations were stated to yield similar, though slightly "slower" evolutions. As we will confirm later on, the configuration is unstable to an ideal MHD instability with Alfvénic growth rates, and we will vary B z0 to model cases at different prevailing plasma beta conditions.…”

Section: Numerical Setupmentioning

confidence: 99%

“…Contrary to both kink and torus instability routes for coronal flux ropes, here we present an as yet underexplored route to violent plasma disruptions where both kink and so-called tilt instabilities (Richard et al 1990) interplay. While only a single flux rope or current channel enters the description in both scenarios discussed above, the tilt instability relates to the basic fact that two adjacent anti-parallel current channels want to repel each other.…”

Section: Introductionmentioning

confidence: 99%

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Interacting Tilt and Kink Instabilities in Repelling Current Channels

Keppens¹,

Porth²,

Xia³

2014

ApJ

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We present a numerical study in resistive magnetohydrodynamics (MHD) where the initial equilibrium configuration contains adjacent, oppositely directed, parallel current channels. Since oppositely directed current channels repel, the equilibrium is liable to an ideal magnetohydrodynamic tilt instability. This tilt evolution, previously studied in planar settings, involves two magnetic islands or flux ropes, which on Alfvénic timescales undergo a combined rotation and separation. This in turn leads to the creation of (near) singular current layers, posing severe challenges to numerical approaches. Using our open-source grid-adaptive MPI-AMRVAC software, we revisit the planar evolution case in compressible MHD, as well as its extension to two-and-a-half-dimensional (2.5D) and full three-dimensional (3D) scenarios. As long as the third dimension can be ignored, pure tilt evolutions result that are hardly affected by out of plane magnetic field components. In all 2.5D runs, our simulations do show secondary tearing type disruptions throughout the near singular current sheets in the far nonlinear saturation regime. In full 3D runs, both current channels can be liable to additional ideal kink deformations. We discuss the effects of having both tilt and kink instabilities acting simultaneously in the violent, reconnection-dominated evolution. In 3D, both the tilt and the kink instabilities can be stabilized by tension forces. As a concrete space plasma application, we argue that interacting tilt-kink instabilities in repelling current channels provide a novel route to initiate solar coronal mass ejections, distinctly different from the currently favored pure kink or torus instability routes.

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Section: Numerical Setupmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Interacting Tilt and Kink Instabilities in Repelling Current Channels

Keppens¹,

Porth²,

Xia³

2014

ApJ

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“…The boundaries in the z-direction are periodic in 3D configurations, whereas in 2.5D the z-direction is invariant. The initially force-free equilibrium is unstable to a tilt instability (Richard et al 1990) and in a 3D configuration also to an additional kink instability bending the field lines with respect to the vertical direction Ripperda et al 2017). Once the instabilities develop and the physics become naturally nonlinear, it allows for fast reconnection of the field lines.…”

Section: Numerical Setupmentioning

confidence: 99%

“…If two of these loops develop antiparallel currents, the tilt instability route to reconnection is accessible . This model was studied in 2D by Richard et al (1990) and extended to 3D by Keppens et al (2014) and Ripperda et al (2017). Here we investigate the effect of an additional kink instability on particle acceleration as well as the effects of boundary conditions, initial conditions and resistivity models on particle dynamics during the full 3D MHD evolution.…”

Section: Introductionmentioning

confidence: 99%

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Reconnection and particle acceleration in interacting flux ropes – II. 3D effects on test particles in magnetically dominated plasmas

Ripperda

Porth

Xia

et al. 2017

Monthly Notices of the Royal Astronomical Society

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We analyze particle acceleration in explosive reconnection events in magnetically dominated proton-electron plasmas. Reconnection is driven by large-scale magnetic stresses in interacting current-carrying flux tubes. Our model relies on development of currentdriven instabilities on macroscopic scales. These tilt-kink instabilities develop in an initially force-free equilibrium of repelling current channels. Using MHD methods we study a 3D model of repelling and interacting flux tubes in which we simultaneously evolve test particles, guided by electromagnetic fields obtained from MHD. We identify two stages of particle acceleration; Initially particles accelerate in the current channels, after which the flux ropes start tilting and kinking and particles accelerate due to reconnection processes in the plasma. The explosive stage of reconnection produces non-thermal energy distributions with slopes that depend on plasma resistivity and the initial particle velocity. We also discuss the influence of the length of the flux ropes on particle acceleration and energy distributions. This study extends previous 2.5D results to 3D setups, providing all ingredients needed to model realistic scenarios like solar flares, black hole flares and particle acceleration in pulsar wind nebulae: formation of strong resistive electric fields, explosive reconnection and non-thermal particle distributions. By assuming initial energy equipartition between electrons and protons, applying low resistivity in accordance with solar corona conditions and limiting the flux rope length to a fraction of a solar radius we obtain realistic energy distributions for solar flares with non-thermal power law tails and maximum electron energies up to 11 MeV and maximum proton energies up to 1 GeV.

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Implicit symmetrized streamfunction formulations of magnetohydrodynamics

Kang

Keyes

2008

Numerical Methods in Fluids

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SUMMARYWe apply the finite element method to the classic tilt instability problem of two-dimensional, incompressible magnetohydrodynamics, using a streamfunction approach to enforce the divergence-free conditions on the magnetic and velocity fields. We compare two formulations of the governing equations, the standard one based on streamfunctions and a hybrid formulation with velocities and magnetic field components. We use a finite element discretization on unstructured meshes and an implicit time discretization scheme. We use the PETSc library with index sets for parallelization. To solve the nonlinear problems on each time step, we compare two nonlinear Gauss-Seidel-type methods and Newton's method with several time-step sizes. We use GMRES in PETSc with multigrid preconditioning to solve the linear subproblems within the nonlinear solvers. We also study the scalability of this simulation on a cluster.

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Magnetic reconnection driven by current repulsion

Cited by 23 publications

References 9 publications

Interacting Tilt and Kink Instabilities in Repelling Current Channels

Interacting Tilt and Kink Instabilities in Repelling Current Channels

Reconnection and particle acceleration in interacting flux ropes – II. 3D effects on test particles in magnetically dominated plasmas

Implicit symmetrized streamfunction formulations of magnetohydrodynamics

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