The nature of separator current layers in MHS equilibria

Stevenson, Julie; Parnell, C. E.; Priest, E. R.; Haynes, A. L.

doi:10.1051/0004-6361/201424348

Cited by 16 publications

(26 citation statements)

References 57 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…It is known that separators are prone to current sheet formation (Lau & Finn 1990;Parnell et al 2010b;Stevenson et al 2015) and thus are likely sites of magnetic reconnection. Theoretical studies of separator reconnection have continued to evolve over many years (e.g.…”

Section: Introductionmentioning

confidence: 99%

Particle acceleration at a reconnecting magnetic separator

Threlfall

Neukirch

Parnell

et al. 2015

A&A

Self Cite

View full text Add to dashboard Cite

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.

show abstract

Section: Introductionmentioning

confidence: 99%

Particle acceleration at a reconnecting magnetic separator

Threlfall

Neukirch

Parnell

et al. 2015

A&A

Self Cite

View full text Add to dashboard Cite

show abstract

“…A separator lies on the boundary of four topologically distinct flux domains (i.e., movement between the domains would result in a discontinuous jump in field line mapping), and so field lines in the vicinity of separators are sensitive to flows across these boundaries. Hence, currents build easily along separators [ Lau and Finn , ; Haynes et al , ; Parnell et al , , ; Stevenson et al , ], and so they are prime locations where 3‐D reconnection occurs.…”

Section: Introductionmentioning

confidence: 99%

“…In this work, we detail the properties of 3‐D separator reconnection in a nondriven experiment, to avoid any such problems, and also where the null points and separator are far from the boundary. The model starts from a MHS equilibrium, containing a separator current layer and excess energy above that of a potential field, formed through the nonresistive relaxation of an initially nonpotential, non–force‐free field, discussed in detail in Stevenson et al []. Reconnection is triggered at the separator current layer using an anomalous diffusivity to mimic the onset of microinstabilities.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Spontaneous reconnection at a separator current layer: 1. Nature of the reconnection

Stevenson

Parnell

2015

JGR Space Physics

Self Cite

View full text Add to dashboard Cite

Magnetic separators, which lie on the boundary between four topologically distinct flux domains, are prime locations in three‐dimensional magnetic fields for reconnection, especially in the magnetosphere between the planetary and interplanetary magnetic fields and also in the solar atmosphere. Little is known about the details of separator reconnection, and so the aim of this paper, which is the first of two, is to study the properties of magnetic reconnection at a single separator. Three‐dimensional, resistive magnetohydrodynamic numerical experiments are run to study separator reconnection starting from a magnetohydrostatic equilibrium which contains a twisted current layer along a single separator linking a pair of opposite‐polarity null points. The resulting reconnection occurs in two phases. The first is short involving rapid reconnection in which the current at the separator is reduced by a factor of around 2.3. Most (75%) of the magnetic energy is converted during this phase, via Ohmic dissipation, directly into internal energy, with just 0.1% going into kinetic energy. During this phase the reconnection occurs along most of the separator away from its ends (the nulls) but in an asymmetric manner which changes both spatially and temporally over time. The second phase is much longer and involves slow impulsive bursty reconnection. Again, Ohmic heating dominates over viscous damping. Here the reconnection occurs in small localized bursts at random anywhere along the separator.

show abstract

“…Lau & Finn 1990;Priest et al 2003;Baumann et al 2013;Parnell et al 2010Parnell et al , 2015Stevenson et al 2015) examining the importance of topological features, such as separators and null points as locations for current build up and reconnection to occur. However, it has also been shown that geometrical features, such as quasi-separatrix layers (QSLs; Priest & Démoulin 1995;Démoulin et al 1996a,b), where the A&A 594, A67 (2016) change in connectivity is continuous but very large, are also locations associated with current formation and energy release (e.g.…”

Section: Introductionmentioning

confidence: 99%

Impact of flux distribution on elementary heating events

O'Hara

Moortel

2016

A&A

View full text Add to dashboard Cite

Context. The complex magnetic field on the solar surface has been shown to contain a range of sizes and distributions of magnetic flux structures. The dynamic evolution of this magnetic carpet by photospheric flows provides a continual source of free magnetic energy into the solar atmosphere, which can subsequently be released by magnetic reconnection. Aims. We investigate how the distribution and number of magnetic flux sources impact the energy release and locations of heating through magnetic reconnection driven by slow footpoint motions. Methods. 3D magnetohydrodynamic (MHD) simulations using Lare3D are carried out, where flux tubes are formed between positive and negative sources placed symmetrically on the lower and upper boundaries of the domain, respectively. The flux tubes are subjected to rotational driving velocities on the boundaries and are forced to interact and reconnect. Results. Initially, simple flux distributions with two and four sources are compared. In both cases, central current concentrations are formed between the flux tubes and Ohmic heating occurs. The reconnection and subsequent energy release is delayed in the foursource case and is shown to produce more locations of heating, but with smaller magnitudes. Increasing the values of the background field between the flux tubes is shown to delay the onset of reconnection and increases the efficiency of heating in both the two-and four-source cases. The cases with two flux tubes are always more energetic than the corresponding four flux tube cases, however the addition of the background field makes this disparity less significant. A final experiment with a larger number of smaller flux sources is considered and the field evolution and energetics are shown to be remarkably similar to the two-source case, indicating the importance of the size and separation of the flux sources relative to the spatial scales of the velocity driver.

show abstract

The nature of separator current layers in MHS equilibria

Cited by 16 publications

References 57 publications

Particle acceleration at a reconnecting magnetic separator

Particle acceleration at a reconnecting magnetic separator

Spontaneous reconnection at a separator current layer: 1. Nature of the reconnection

Impact of flux distribution on elementary heating events

Contact Info

Product

Resources

About