Three-dimensional magnetic reconnection in astrophysical plasmas

Li, Ting; Priest, E. R.; Guo, Ruilong

doi:10.1098/rspa.2020.0949

Cited by 28 publications

(14 citation statements)

References 161 publications

(335 reference statements)

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“…The energy release mechanism of the three simulated microflares is similar to that for major flares. In the standard CME/flare model, the magnetic energy is believed to be efficiently released through magnetic reconnection, where the current density and Q values are large (e.g., Sui & Holman 2003;Li et al 2021). Moreover, the reconnection can drive two oppositely directed outflows along the orientation roughly perpendicular to the converging inflows.…”

Section: Summary and Discussionmentioning

confidence: 99%

Three-dimensional Magnetic and Thermodynamic Structures of Solar Microflares

Cheng

Chen

et al. 2022

ApJL

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Microflares, one of the small-scale solar activities, are believed to be caused by magnetic reconnection. Nevertheless, their three-dimensional (3D) magnetic structures, thermodynamic structures, and physical links to reconnection are unclear. In this Letter, based on a high-resolution 3D radiative magnetohydrodynamic simulation of the quiet Sun spanning from the upper convection zone to the corona, we investigate the 3D magnetic and thermodynamic structures of three homologous microflares. It is found that they originate from localized hot plasma embedded in the chromospheric environment at the height of 2–10 Mm above the photosphere and last for 3–10 minutes with released magnetic energy in the range of 1027–1028 erg. The heated plasma is almost cospatial with the regions where the heating rate per particle is maximal. The 3D velocity field reveals a pair of converging flows with velocities of tens of km s−1 moving toward and outflows with velocities of about 100 km s−1 moving away from the hot plasma. These features support magnetic reconnection playing a critical role in heating the localized chromospheric plasma to coronal temperature, giving rise to the observed microflares. The magnetic topology analysis further discloses that the reconnection region is located near quasi-separators where both current density and squashing factors are maximal although the specific topology may vary from a tether-cutting to fan-spine-like structure.

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Section: Summary and Discussionmentioning

confidence: 99%

Three-dimensional Magnetic and Thermodynamic Structures of Solar Microflares

Cheng

Chen

et al. 2022

ApJL

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“…For "Type I" confined flares, the slipping motions of flare loops and ribbon substructures are the signatures of slipping reconnections along the QSLs (Aulanier et al 2012;Janvier et al 2013). Flipping or slipping of magnetic fields was predicted to be a property of all 3D reconnection models (Priest & Forbes 1992;Li et al 2021b), due to the continuous change of field line connections during their passage through a diffusion region. The slipping motions of flare loops and ribbon substructures have been reported during eruptive flares Dudík et al 2016), which can be interpreted by the standard flare model in 3D (Janvier et al 2015).…”

Section: Summary and Discussionmentioning

confidence: 99%

Dynamic Property and Magnetic Nonpotentiality of Two Types of Confined Solar Flares

Jing

2022

ApJ

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We analyze 152 large confined flares (GOES class ≥ M1.0 and ≤ 45° from disk center) during 2010−2019, and classify them into two types according to the criterion taken from the work of Li et al. “Type I” flares are characterized by slipping motions of flare loops and ribbons and a stable filament underlying the flare loops. “Type II” flares are associated with the failed eruptions of the filaments, which can be explained by the classical 2D flare model. A total of 59 flares are “Type I” flares (about 40%) and 93 events are “Type II” flares (about 60%). There are significant differences in distributions of the total unsigned magnetic flux (ΦAR) of active regions (ARs) producing the two types of confined flares, with “Type I” confined flares from ARs with a larger ΦAR than “Type II.” We calculate the mean shear angle ΨHFED within the core of an AR prior to the flare onset, and find that it is slightly smaller for “Type I” flares than that for “Type II” events. The relative nonpotentiality parameter ΨHFED/ΦAR has the best performance in distinguishing the two types of flares. About 73% of “Type I” confined flares have ΨHFED/ΦAR<1.0 × 10−21 degree Mx−1, and about 66% of “Type II” confined events have ΨHFED/ΦAR ≥ 1.0 × 10−21 degree Mx−1. We suggest that “Type I” confined flares cannot be explained by the standard flare model in 2D/3D, and the occurrence of multiple slipping magnetic reconnections within the complex magnetic systems probably leads to the observed flare.

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“…A related topic discussed in a series of recent papers, but beyond the coverage of this Roadmap, is about stochastic field lines which can separate rapidly in large 3D turbulent systems 166 to lose their connectivity such that reconnection is spontaneously achieved 167 , but without apparent current sheets. Magnetic reconnection involves 3D null points is a further advanced subtopic 168 whose roles in understanding 32/35 explosive reconnection is yet to be fully explored 169 .…”

Section: Author Contributionsmentioning

confidence: 99%

“…• How does reconnection take place in three dimensions, in both quasi-2D current sheets (Box 1) and in fully 3D geometries 169 ?…”

Section: Author Contributionsmentioning

confidence: 99%

Magnetic reconnection in the era of exascale computing and multiscale experiments

Ji,

Daughton,

Jara-Almonte

et al. 2022

Preprint

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Astrophysical plasmas have the remarkable ability to preserve magnetic topology, which inevitably gives rise to the accumulation of magnetic energy within stressed regions including current sheets. This stored energy is often released explosively through the process of magnetic reconnection, which produces a reconfiguration of the magnetic field, along with high-speed flows, thermal heating, and nonthermal particle acceleration. Either collisional or kinetic dissipation mechanisms are required to overcome the topological constraints, both of which have been predicted by theory and validated with in situ spacecraft observations or laboratory experiments. However, major challenges remain in understanding magnetic reconnection in large systems, such as the solar corona, where the collisionality is weak and the kinetic scales are vanishingly small in comparison to macroscopic scales. The plasmoid instability or formation of multiple plasmoids in long reconnecting current sheets is one possible multiscale solution for bridging this vast range of scales, and new laboratory experiments are poised to study these regimes. In conjunction with these efforts, we anticipate that the coming era of exascale computing, together with the next generation of observational capabilities, will enable new progress on a range of challenging problems, including the energy build-up and onset of reconnection, partially ionized regimes, the influence of magnetic turbulence, and particle acceleration.Website summary: Magnetic reconnection explosively releases stored magnetic energy in astrophysical plasmas. Thanks to advances in observations, exascale computing and multiscale experiments, it will be possible to solve outstanding physics problems, including the immense separation between global and dissipation scales, reconnection onset, and particle acceleration.

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Three-dimensional magnetic reconnection in astrophysical plasmas

Cited by 28 publications

References 161 publications

Three-dimensional Magnetic and Thermodynamic Structures of Solar Microflares

Three-dimensional Magnetic and Thermodynamic Structures of Solar Microflares

Dynamic Property and Magnetic Nonpotentiality of Two Types of Confined Solar Flares

Magnetic reconnection in the era of exascale computing and multiscale experiments

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