Dynamic Three‐dimensional Reconnection in a Separator Geometry with Two Null Points

Pontin, D. I.; Craig, I. J. D.

doi:10.1086/500725

Cited by 24 publications

(19 citation statements)

References 30 publications

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“…In our example, E 0 = E z (0, 0, 0) = Φ nid0 /(2b) = ηj 0 , where j 0 =j 0 B 0 /(µL 0 ) is the value of the current at the origin, and along the spine (13) implies that…”

Section: Torsional Spine Reconnectionmentioning

confidence: 88%

“…Thus, after putting (R, z)=(a, z s ) in the expression (13) for Φ that holds in the diffusion region, we obtain…”

Section: Torsional Spine Reconnectionmentioning

confidence: 99%

“…A key point is that in three dimensions reconnection occurs where a component of the electric field parallel to the magnetic field is present -and this can be in many different field configurations. For example, reconnection may occur either at null points [e.g., [6][7][8][9][10][11][12][13] or in the absence of null points at quasi-separatrix layers or hyperbolic flux tubes [14][15][16][17][18][19][20][21][22][23] or it may occur along separators that join one null point to another [7,[24][25][26][27][28][29][30][31].…”

Section: Introductionmentioning

confidence: 99%

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Three-dimensional null point reconnection regimes

2009

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Recent advances in theory and computational experiments have shown the need to refine the previous categorisation of magnetic reconnection at three-dimensional null points -points at which the magnetic field vanishes. We propose here a division into three different types, depending on the nature of the flow near the spine and fan of the null. The spine is an isolated field line which approaches the null (or recedes from it), while the fan is a surface of field lines which recede from it (or approach it).So-called torsional spine reconnection occurs when field lines in the vicinity of the fan rotate, with current becoming concentrated along the spine, so that nearby field lines undergo rotational slippage. In torsional fan reconnection field lines near the spine rotate and create a current that is concentrated in the fan with a rotational flux mismatch and rotational slippage. In both of these regimes, the spine and fan are perpendicular and there is no flux transfer across spine or fan. The third regime, called spine-fan reconnection, is the most common in practice and combines elements of the previous spine and fan models. In this case, in response to a generic shearing motion, the null point collapses to form a current sheet that is focused at the null itself, in a sheet that locally spans both the spine and fan. In this regime the spine and fan are no longer perpendicular and there is flux transfer across both of them.

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“…In our example, E 0 = E z (0, 0, 0) = Φ nid0 /(2b) = ηj 0 , where j 0 =j 0 B 0 /(µL 0 ) is the value of the current at the origin, and along the spine (13) implies that…”

Section: Torsional Spine Reconnectionmentioning

confidence: 88%

“…Thus, after putting (R, z)=(a, z s ) in the expression (13) for Φ that holds in the diffusion region, we obtain…”

Section: Torsional Spine Reconnectionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Three-dimensional null point reconnection regimes

2009

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“…Lau & Finn 1990;Priest & Pontin 2009), magnetic separators (which connect two null-points, e.g. Longcope & Cowley 1996;Pontin & Craig 2006;Haynes et al 2007), or may occur in the absence of any such topological features (Schindler et al 1988), the latter sometimes termed "non-null reconnection". In particular, the local magnetic field structure need not be hyperbolic but may be elliptic (Hornig & Priest 2003), as recently found in some 3D numerical simulations of reconnection.…”

Section: Plasma Flows and Reconnectionmentioning

confidence: 99%

Dynamics of braided coronal loops

Wilmot-Smith¹,

Pontin²,

Hornig³

2010

A&A

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Aims. The response of the solar coronal magnetic field to small-scale photospheric boundary motions including the possible formation of current sheets via the Parker scenario is one of open questions of solar physics. Here we address the problem via a numerical simulation. Methods. The three-dimensional evolution of a braided magnetic field which is initially close to a force-free state is followed using a resistive MHD code. Results. A long-wavelength instability takes place and leads to the formation of two thin current layers. Magnetic reconnection occurs across the current sheets with three-dimensional features shown, including an elliptic magnetic field structure about the reconnection site, and results in an untwisting of the global field structure.

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“…Theoretical studies of separator reconnection have continued to evolve over many years (e.g. Sonnerup 1979;Lau & Finn 1990;Longcope & Cowley 1996;Galsgaard et al 2000;Longcope 2001;Pontin & Craig 2006;Parnell et al 2008;Dorelli & Bhattacharjee 2008). Building on experiments by Haynes et al (2007) and Parnell (2007), recent work has highlighted that multiple magnetic separators may exist within a given magnetic environment at any given time (Parnell et al 2010a) and that separator reconnection is an important and fundamental process when emerging magnetic flux interacts with overlying magnetic field (Parnell et al 2010b).…”

Section: Introductionmentioning

confidence: 99%

Particle acceleration at a reconnecting magnetic separator

Threlfall

Neukirch

Parnell

et al. 2015

A&A

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Context. While the exact acceleration mechanism of energetic particles during solar flares is (as yet) unknown, magnetic reconnection plays a key role both in the release of stored magnetic energy of the solar corona and the magnetic restructuring during a flare. Recent work has shown that special field lines, called separators, are common sites of reconnection in 3D numerical experiments. To date, 3D separator reconnection sites have received little attention as particle accelerators. Aims. We investigate the effectiveness of separator reconnection as a particle acceleration mechanism for electrons and protons. Methods. We study the particle acceleration using a relativistic guiding-centre particle code in a time-dependent kinematic model of magnetic reconnection at a separator. Results. The effect upon particle behaviour of initial position, pitch angle, and initial kinetic energy are examined in detail, both for specific (single) particle examples and for large distributions of initial conditions. The separator reconnection model contains several free parameters, and we study the effect of changing these parameters upon particle acceleration, in particular in view of the final particle energy ranges that agree with observed energy spectra.

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Dynamic Three‐dimensional Reconnection in a Separator Geometry with Two Null Points

Cited by 24 publications

References 30 publications

Three-dimensional null point reconnection regimes

Three-dimensional null point reconnection regimes

Dynamics of braided coronal loops

Particle acceleration at a reconnecting magnetic separator

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