Particle acceleration at a three-dimensional   reconnection site 
in the solar corona

Dalla, S.; Browning, Philippa

doi:10.1051/0004-6361:20042589

Cited by 86 publications

(99 citation statements)

References 24 publications

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“…15 and further studied by Ref. 18. Particles which travel very close to the null point gain the most energy since they are directly accelerated by the electric field there.…”

Section: A Case I: Sheared Magnetic Profilementioning

confidence: 99%

“…18 Reference 14 performed numerical simulations of the non-relativistic particle motion in an X-type magnetic null configuration and found that particle trajectories in the non-adiabatic region close to the null are chaotic a) a.d.gascoyne@sheffield.ac.uk in nature and quantified this by calculating a positive value for the maximum Lyapunov exponent.…”

Section: Introductionmentioning

confidence: 99%

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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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“…15 and further studied by Ref. 18. Particles which travel very close to the null point gain the most energy since they are directly accelerated by the electric field there.…”

Section: A Case I: Sheared Magnetic Profilementioning

confidence: 99%

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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“…Numerical simulations of magnetic reconnection in null-points in astrophysical and space plasmas were performed with MHD (Galsgaard & Nordlund 1997;Galsgaard & Pontin 2011) and kinetic (Baumann & Nordlund 2012) codes. The testparticle studies by Dalla & Browning (2005); Stanier et al (2012) found that null-points were able to accelerate particles to the energies, observed in solar flares.…”

Section: Introductionmentioning

confidence: 99%

Role of Z-pinches in magnetic reconnection in space plasmas

2014

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A widely accepted scenario of magnetic reconnection in collisionless space plasmas is the breakage of magnetic field lines in X-points. In laboratory, reconnection is commonly studied in pinches, current channels embedded into twisted magnetic fields. No model of magnetic reconnection in space plasmas considers both null-points and pinches as peers. We have performed a particle-in-cell simulation of magnetic reconnection in a three-dimensional configuration where null-points are present initially, and Z-pinches are formed during the simulation along the lines of spiral null-points. The non-spiral nullpoints are more stable than spiral ones, and no substantial energy dissipation is associated with them. On the contrary, turbulent magnetic reconnection in the pinches causes the magnetic energy to decay at a rate of ∼ 1.5% per ion gyro period. Dissipation in similar structures is a likely scenario in space plasmas with large fraction of spiral null-points.

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“…When considered in isolation (depending on how the reconnection itself proceeds), various effects including drifting, mirroring, and acceleration have been studied in reference to both protons and electrons in a number of different experiments (e.g. Dalla and Browning, 2005, 2008Stanier, Browning, and Dalla, 2012). In our experiment, we see no evidence of mirroring and a minimal impact of drifts.…”

Section: Comparison With Topological Reconnection Modelsmentioning

confidence: 79%

“…Examples include several regimes of 3D null-point reconnection (e.g. Dalla and Browning, 2005, 2008Guo et al, 2010;Stanier, Browning, and Dalla, 2012), magnetic separator reconnection (e.g. Threlfall et al, 2015Threlfall et al, , 2016a or reconnection at fragmented current sheets (e.g.…”

Section: Introductionmentioning

confidence: 99%

Particle Acceleration Due to Coronal Non-null Magnetic Reconnection

2017

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Various topological features, for example magnetic null points and separators, have been inferred as likely sites of magnetic reconnection and particle acceleration in the solar atmosphere. In fact, magnetic reconnection is not constrained to solely take place at or near such topological features and may also take place in the absence of such features. Studies of particle acceleration using non-topological reconnection experiments embedded in the solar atmosphere are uncommon. We aim to investigate and characterise particle behaviour in a model of magnetic reconnection which causes an arcade of solar coronal magnetic field to twist and form an erupting flux rope, crucially in the absence of any common topological features where reconnection is often thought to occur. We use a numerical scheme that evolves the gyro-averaged orbit equations of single electrons and protons in time and space, and simulate the gyromotion of particles in a fully analytical global field model. We observe and discuss how the magnetic and electric fields of the model and the initial conditions of each orbit may lead to acceleration of protons and electrons up to 2 MeV in energy (depending on model parameters). We describe the morphology of time-dependent acceleration and impact sites for each particle species and compare our findings to those recovered by topologically based studies of three-dimensional (3D) reconnection and particle acceleration. We also broadly compare aspects of our findings to general observational features typically seen during two-ribbon flare events.

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Particle acceleration at a three-dimensional reconnection site in the solar corona

Cited by 86 publications

References 24 publications

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

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

Role of Z-pinches in magnetic reconnection in space plasmas

Particle Acceleration Due to Coronal Non-null Magnetic Reconnection

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