Three-dimensional null point reconnection regimes

Priest, E. R.; Pontin, D. I.

doi:10.1063/1.3257901

Cited by 140 publications

(144 citation statements)

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“…The reconnection triggered is different in all three cases. A comprehensive review of three-dimensional null-point reconnection can be found in Priest & Pontin [46] and Pontin et al [47]. Examples of solar scenarios in which reconnection has been triggered at null points by boundary driving include work by Aulanier et al [48], Pariat et al [49], Masson et al [50,51], but these cases are all aimed at modelling coronal mass ejections (CMEs) or explosive events, such as solar flares, rather than studying coronal heating.…”

Section: (A) Behaviour Of Wave Pulses At Topological Featuresmentioning

confidence: 99%

“…Owing to the additional complexity that the third dimension brings, in three dimensions, the specifics of the boundary perturbation can cause a variety of different current accumulations that are associated with different types of reconnection [46]. In particular, a three-dimensional potential null point's spine is orthogonal to its separatrix surface.…”

Section: (A) Behaviour Of Wave Pulses At Topological Featuresmentioning

confidence: 99%

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Is magnetic topology important for heating the solar atmosphere?

Parnell

Stevenson

Threlfall

et al. 2015

Phil. Trans. R. Soc. A.

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Magnetic fields permeate the entire solar atmosphere weaving an extremely complex pattern on both local and global scales. In order to understand the nature of this tangled web of magnetic fields, its magnetic skeleton, which forms the boundaries between topologically distinct flux domains, may be determined. The magnetic skeleton consists of null points, separatrix surfaces, spines and separators. The skeleton is often used to clearly visualize key elements of the magnetic configuration, but parts of the skeleton are also locations where currents and waves may collect and dissipate. In this review, the nature of the magnetic skeleton on both global and local scales, over solar cycle time scales, is explained. The behaviour of wave pulses in the vicinity of both nulls and separators is discussed and so too is the formation of current layers and reconnection at the same features. Each of these processes leads to heating of the solar atmosphere, but collectively do they provide enough heat, spread over a wide enough area, to explain the energy losses throughout the solar atmosphere? Here, we consider this question for the three different solar regions: active regions, open-field regions and the quiet Sun. We find that the heating of active regions and open-field regions is highly unlikely to be due to reconnection or wave dissipation at topological features, but it is possible that these may play a role in the heating of the quiet Sun. In active regions, the absence of a complex topology may play an important role in allowing large energies to build up and then, subsequently, be explosively released in the form of a solar flare. Additionally, knowledge of the intricate boundaries of open-field regions (which the magnetic skeleton provides) could be very important in determining the main acceleration mechanism(s) of the solar wind.

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Section: (A) Behaviour Of Wave Pulses At Topological Featuresmentioning

confidence: 99%

Section: (A) Behaviour Of Wave Pulses At Topological Featuresmentioning

confidence: 99%

Is magnetic topology important for heating the solar atmosphere?

Parnell

Stevenson

Threlfall

et al. 2015

Phil. Trans. R. Soc. A.

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“…The eigenvalues of the magnetic field gradient B  define whether a null is radial (degenerates into an Xpoint in 2D) or spiral (degenerates into an O-point; Lau & Finn 1990;Parnell et al 1996). In the magnetohydrodynamic (MHD) approximation the theory of magnetic reconnection at null points has been derived by Pontin et al (2004) andPontin & Galsgaard (2007), and reconnection regimes were classified and generalized by Priest & Pontin (2009. Isolated magnetic nulls have been studied by means of MHD ) and kinetic particle-in-cell (PIC; Baumann & Nordlund 2012) simulations.…”

Section: Introductionmentioning

confidence: 99%

Magnetic Null Points in Kinetic Simulations of Space Plasmas

Olshevsky

Deca

Divin

et al. 2016

ApJ

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We present a systematic attempt to study magnetic null points and the associated magnetic energy conversion in kinetic particle-in-cell simulations of various plasma configurations. We address three-dimensional simulations performed with the semi-implicit kinetic electromagnetic code iPic3D in different setups: variations of a Harris current sheet, dipolar and quadrupolar magnetospheres interacting with the solar wind,and a relaxing turbulent configuration with multiple null points. Spiral nulls are more likely created in space plasmas: in all our simulations except lunar magnetic anomaly (LMA) and quadrupolar mini-magnetosphere the number of spiral nulls prevails over the number of radial nulls by a factor of 3-9. We show that often magnetic nulls do not indicate the regions of intensive energy dissipation. Energy dissipation events caused by topological bifurcations at radial nulls are rather rare and short-lived. The so-called X-lines formed by the radial nulls in the Harris current sheet and LMA simulations are rather stable and do not exhibit any energy dissipation. Energy dissipation is more powerful in the vicinity of spiral nulls enclosed by magnetic flux ropes with strong currents at their axes (their crosssections resemble 2D magnetic islands). These null lines reminiscent of Z-pinches efficiently dissipate magnetic energy due to secondary instabilities such as the two-stream or kinking instability, accompanied by changes in magnetic topology. Current enhancements accompanied by spiral nulls may signal magnetic energy conversion sites in the observational data.

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“…23,24 The other 3D null point reconnection regimes developed are the sheared spine/ fan and the torsional spine/fan reconnection regimes. 1,2 In the sheared spine/fan case, generic shearing occurs across either the spine axis, fan plane, or both, resulting in a current sheet at the null point which is localised to either the spine, fan plane, or both depending on the location of the shear. In the torsional spine/fan case, field lines in the vicinity of the fan/spine rotate causing current to become concentrated along the spine/fan.…”

Section: Introductionmentioning

confidence: 99%

Dynamics of charged particle motion in the vicinity of three dimensional magnetic null points: Energization and chaos

Gascoyne

2015

Physics of Plasmas

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Using a full orbit test particle approach, we analyse the motion of a single proton in the vicinity of magnetic null point configurations which are solutions to the kinematic, steady state, resistive magnetohydrodynamics equations. We consider two magnetic configurations, namely, the sheared and torsional spine reconnection regimes [E. R. Priest and D. I. Pontin, Phys. Plasmas 16, 122101 (2009); P. Wyper and R. Jain, Phys. Plasmas 17, 092902 (2010)]; each produce an associated electric field and thus the possibility of accelerating charged particles to high energy levels, i.e., > MeV, as observed in solar flares [R. P. Lin, Space Sci. Rev. 124, 233 (2006)]. The particle's energy gain is strongly dependent on the location of injection and is characterised by the angle of approach b, with optimum angle of approach b opt as the value of b which produces the maximum energy gain. We examine the topological features of each regime and analyse the effect on the energy gain of the proton. We also calculate the complete Lyapunov spectrum for the considered dynamical systems in order to correctly quantify the chaotic nature of the particle orbits. We find that the sheared model is a good candidate for the acceleration of particles, and for increased shear, we expect a larger population to be accelerated to higher energy levels. In the strong electric field regime (E 0 ¼ 1500 V/m), the torsional model produces chaotic particle orbits quantified by the calculation of multiple positive Lyapunov exponents in the spectrum, whereas the sheared model produces chaotic orbits only in the neighbourhood of the null point. V C 2015 AIP Publishing LLC.

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Three-dimensional null point reconnection regimes

Cited by 140 publications

References 73 publications

Is magnetic topology important for heating the solar atmosphere?

Is magnetic topology important for heating the solar atmosphere?

Magnetic Null Points in Kinetic Simulations of Space Plasmas

Dynamics of charged particle motion in the vicinity of three dimensional magnetic null points: Energization and chaos

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