Quasi-separatrix layers and three-dimensional reconnection diagnostics for line-tied tearing modes

Richardson, A. S.; Finn, John M.

doi:10.1016/j.cnsns.2011.04.029

Cited by 12 publications

(22 citation statements)

References 25 publications

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“…These works highlight the key role of magnetic separator surfaces, surfaces across which the field line connectivity changes discontinuously. The role of separator surfaces as likely sites for current sheet formation and reconnection has been further generalized to systems that lack null points through the introduction of quasi-separatrix layers (QSLs) [44][45][46]. QSLs have been identified in the LAPD experiment and in kinetic simulations of line-tied reconnection [47].…”

Section: (B) Reconnection In Line-tied Magnetic Fieldsmentioning

confidence: 99%

Perspectives on magnetic reconnection

Zweibel

Yamada

2016

Proc. R. Soc. A.

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Magnetic reconnection is a topological rearrangement of magnetic field that occurs on time scales much faster than the global magnetic diffusion time. Since the field lines break on microscopic scales but energy is stored and the field is driven on macroscopic scales, reconnection is an inherently multi-scale process that often involves both magnetohydrodynamic (MHD) and kinetic phenomena. In this article, we begin with the MHD point of view and then describe the dynamics and energetics of reconnection using a two-fluid formulation. We also focus on the respective roles of global and local processes and how they are coupled. We conclude that the triggers for reconnection are mostly global, that the key energy conversion and dissipation processes are either local or global, and that the presence of a continuum of scales coupled from microscopic to macroscopic may be the most likely path to fast reconnection.

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Section: (B) Reconnection In Line-tied Magnetic Fieldsmentioning

confidence: 99%

Perspectives on magnetic reconnection

Zweibel

Yamada

2016

Proc. R. Soc. A.

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“…The computation of this indicator is of similar complexity to the identification of null points but detects also other types of more complex 3D reconnnection topologies. The new indicator is simpler compared to other methods to find these complex 3D magnetic reconnection topologies such as the squashing factor (Titov et al 2002;Finn et al 2014) and the field integrated parallel potential (Lau & Finn 1990;Richardson & Finn 2012) that requires complex integration along the field lines and even of the agyrotropy (Scudder & Daughton 2008) that requires one to compute the eigenvalues of the pressure tensor. The proposed indicator is a local operation that requires only the knowledge of the local magnetic and electric field: it can be applied in a simulation or in observational data from a field instrument.…”

Section: Introductionmentioning

confidence: 99%

Detecting Reconnection Sites Using the Lorentz Transformations for Electromagnetic Fields

Lapenta

2021

ApJ

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We take a pragmatic definition of reconnection to find locations where a reconnection electric field causes a E × B drift that carries two components of the magnetic field towards their elimination. With this in mind as our target, we observe that such locations can be found using a new indicator: the velocity of the Lorentz transformation that eliminates two components of the local magnetic field. Serendipitously, the indicator naturally becomes subluminal in the close proximity of a point where two components of the magnetic field vanish and it is hard zero at the vanishing location. Everywhere else the velocity of this Lorentz frame change far exceeds the speed of light. This property can be quickly applied in practice because computing the frame change is a local operation that requires only the knowledge of the local magnetic and electric field: it can be applied in a simulation or in observational data from a field instrument. We further show that the points identified can be classified in 6 categories that extend the usual types of magnetic nulls to the case of 3D reconnection in presence of a guide field. The approach is used to identify secondary electron scale reconnection sites in a turbulent outflow from a primary reconnection site in a highly resolved massively parallel fully kinetic particle in cell simulation. Numerous points are found and their detailed analysis is reported.

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“…QSLs are the locations where these non-idealnesses can occur; therefore, the two approaches are complementary (Démoulin et al 1996b;Richardson & Finn 2012).…”

Section: Introductionmentioning

confidence: 99%

Parallel Evolution of Quasi-Separatrix Layers and Active Region Upflows

Mandrini

Baker²,

Démoulin

et al. 2015

ApJ

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Persistent plasma upflows were observed with Hinode's EUV Imaging Spectrometer (EIS) at the edges of active region (AR) 10978 as it crossed the solar disk. We analyze the evolution of the photospheric magnetic and velocity fields of the AR, model its coronal magnetic field, and compute the location of magnetic null-points and quasisepratrix layers (QSLs) searching for the origin of EIS upflows. Magnetic reconnection at the computed null points cannot explain all of the observed EIS upflow regions. However, EIS upflows and QSLs are found to evolve in parallel, both temporarily and spatially. Sections of two sets of QSLs, called outer and inner, are found associated to EIS upflow streams having different characteristics. The reconnection process in the outer QSLs is forced by a large-scale photospheric flow pattern which is present in the AR for several days. We propose a scenario in which upflows are observed provided a large enough asymmetry in plasma pressure exists between the pre-reconnection loops and for as long as a photospheric forcing is at work. A similar mechanism operates in the inner QSLs; in this case, it is forced by the emergence and evolution of the bipoles between the two main AR polarities. Our findings provide strong support to the results from previous individual case studies investigating the role of magnetic reconnection at QSLs as the origin of the upflowing plasma. Furthermore, we propose that persistent reconnection along QSLs does not only drive the EIS upflows, but it is also responsible for a continuous metric radio noise-storm observed in AR 10978 along its disk transit by the Nançay Radio Heliograph.

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Quasi-separatrix layers and three-dimensional reconnection diagnostics for line-tied tearing modes

Cited by 12 publications

References 25 publications

Perspectives on magnetic reconnection

Perspectives on magnetic reconnection

Detecting Reconnection Sites Using the Lorentz Transformations for Electromagnetic Fields

Parallel Evolution of Quasi-Separatrix Layers and Active Region Upflows

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