Unsteady magnetic reconnection in non-periodic multiple current sheets

1998 ◽  
Vol 43 (3) ◽  
pp. 245-249
Author(s):  
Yifan Liu ◽  
Xiaohu Wang ◽  
Huinan Zheng ◽  
Shui Wang
Keyword(s):  
Magnetic Reconnection ◽  
Current Sheets

Manifestation of magnetic reconnection in coronal streamer current sheets

1994 ◽  
Vol 70 (1-2) ◽  
pp. 299-302 ◽  
Author(s):  
A. I. Verneta ◽  
E. Antonucci ◽  
D. Marocchi
Keyword(s):  
Magnetic Reconnection ◽  
Current Sheets ◽  
Coronal Streamer

Evolution of electron current sheets in collisionless magnetic reconnection

2015 ◽  
Vol 22 (10) ◽  
pp. 102110 ◽  
Author(s):  
Neeraj Jain ◽  
A. Surjalal Sharma
Keyword(s):  
Magnetic Reconnection ◽  
Electron Current ◽  
Current Sheets

Current sheets, magnetic islands and associated particle acceleration in the solar wind as observed by Ulysses near the ecliptic plane

2020 ◽  
Author(s):  
Olga Malandraki ◽  
Olga Khabarova ◽  
Roberto Bruno ◽  
Gary Zank ◽  
Gang Li and the ISSI-405 team
Keyword(s):  
Solar Wind ◽  
Particle Acceleration ◽  
Magnetic Reconnection ◽  
Energetic Particle ◽  
Particle Flux ◽  
Energetic Particles ◽  
Magnetic Islands ◽  
Intermittent Turbulence ◽  
Current Sheets ◽  
Energetic Particle Flux

<p>Recent studies of particle acceleration in the heliosphere have revealed a new mechanism that can locally energize particles up to several MeV/nuc. Stream-stream interactions as well as the heliospheric current sheet – stream interactions lead to formation of large magnetic cavities, bordered by strong current sheets (CSs), which in turn produce secondary CSs and dynamical small-scale magnetic islands (SMIs) of ~0.01AU or less owing to magnetic reconnection. It has been shown that particle acceleration or re-acceleration occurs via stochastic magnetic reconnection in dynamical SMIs confined inside magnetic cavities observed at 1 AU. The study links the occurrence of CSs and SMIs with characteristics of intermittent turbulence and observations of energetic particles of keV-MeV/nuc energies at ~5.3 AU. We analyze selected samples of different plasmas observed by Ulysses during a widely discussed event, which was characterized by a series of high-speed streams of various origins that interacted beyond the Earth’s orbit in January 2005. The interactions formed complex conglomerates of merged interplanetary coronal mass ejections, stream/corotating interaction regions and magnetic cavities. We study properties of turbulence and associated structures of various scales. We confirm the importance of intermittent turbulence and magnetic reconnection in modulating solar energetic particle flux and even local particle acceleration. Coherent structures, including CSs and SMIs, play a significant role in the development of secondary stochastic particle acceleration, which changes the observed energetic particle flux time-intensity profiles and increases the final energy level to which energetic particles can be accelerated in the solar wind.</p>

The Relationship Between Electron-Only Magnetic Reconnection and Turbulence in Earth’s Magnetosheath

2020 ◽  
Author(s):  
Julia E. Stawarz ◽  
Jonathan P. Eastwood ◽  
Tai Phan ◽  
Imogen L. Gingell ◽  
Alfred Mallet ◽  
...  
Keyword(s):  
Magnetic Reconnection ◽  
Power Spectra ◽  
Theoretical Work ◽  
Small Scale ◽  
Current Sheets ◽  
The Earth ◽  
Recent Theoretical Work ◽  
Magnetospheric Multiscale ◽  
Scale Turbulence ◽  
The Relationship

<p>The Earth’s magnetosheath is filled with small-scale current sheets arising from turbulent dynamics in the plasma. Previous observations and simulations have provided evidence that such current sheets can be sites for magnetic reconnection. Recently, observations from the Magnetospheric Multiscale (MMS) mission have revealed that a novel form of “electron-only” reconnection can occur at these small-scale, turbulence-driven current sheets, in which ions do not appear to couple to the reconnected magnetic field to form ion jets. The presence of electron-only reconnection may facilitate dissipation of the turbulence, thereby influencing the partition of energy between ions and electrons, and can alter the nonlinear dynamics of the turbulence itself. In this study, we perform a survey of turbulent intervals in the Earth’s magnetosheath as observed by MMS in order to determine how common magnetic reconnection is in the turbulent magnetosheath and how it impacts the small-scale turbulent dynamics. The magnetic correlation length, which dictates the length of the turbulent current sheets, is short enough in most of the examined intervals for reconnection with reduced or absent ion jets to occur. Magnetic reconnection is found to be a common feature within these intervals, with a significant fraction of reconnecting current sheets showing evidence of sub-Alfvénic ion jets and super- Alfvénic electron jets, consistent with electron-only reconnection. Moreover, a subset of the intervals exhibit changes in the behavior of the small-scale magnetic power spectra, which may be related to the reconnecting current sheets. The results of the survey are compared with recent theoretical work on electron-only reconnection in turbulent plasmas.</p>

Effect of plasma-β on the onset of plasmoid instability in Sweet–Parker current sheets

2014 ◽  
Vol 80 (5) ◽  
pp. 655-665 ◽  
Author(s):  
H. Baty
Keyword(s):  
Magnetic Reconnection ◽  
Temperature Increase ◽  
Numerical Study ◽  
Two Dimensional ◽  
Magnetic Island ◽  
Current Sheets ◽  
A Value ◽  
Similar Dependence ◽  
Definition Of ◽  
Local Temperature Increase

AbstractA numerical study of magnetic reconnection in two-dimensional resistive magnetohydrodynamics for Sweet–Parker current sheets that are subject to plasmoid instability is carried out. The effect of the initial upstream plasma-β on the critical Lundquist number Sc for the onset of plasmoid instability is studied. Our results indicate a weak dependence, with a value of Sc ≃ 1.5 × 104 in the limit of zero β, and a value of Sc ≃ 1 × 104 in the opposite high β regime (β ≫ 1). A similar dependence was previously obtained (Ni et al. 2012 Phys. Plasm. 19, 072902), but with a somewhat much larger variation, that can be largely attributed to the different configuration setup used in their study, and also to the definition of the Lundquist number. This conclusion does not depend significantly on the equilibrium used, i.e. both initial configurations with either plasma density or temperature spatial variations lead to very similar results. Finally, we show that the inner plasmoid structure appears as an under-dense hotted magnetic island, with a local temperature increase that is noticeably strengthened for low β cases.

scholarly journals Shock heating in numerical simulations of kink-unstable coronal loops

2015 ◽  
Vol 373 (2042) ◽  
pp. 20140266 ◽  
Author(s):  
M. R. Bareford ◽  
A. W. Hood
Keyword(s):  
Magnetic Reconnection ◽  
Large Scale ◽  
Magnetic Energy ◽  
Coronal Loops ◽  
Current Sheets ◽  
Shock Heating ◽  
Strong Current ◽  
Coronal Magnetic Fields ◽  
Magnetohydrodynamic Simulations ◽  
The Magnetic Field

An analysis of the importance of shock heating within coronal magnetic fields has hitherto been a neglected area of study. We present new results obtained from nonlinear magnetohydrodynamic simulations of straight coronal loops. This work shows how the energy released from the magnetic field, following an ideal instability, can be converted into thermal energy, thereby heating the solar corona. Fast dissipation of magnetic energy is necessary for coronal heating and this requirement is compatible with the time scales associated with ideal instabilities. Therefore, we choose an initial loop configuration that is susceptible to the fast-growing kink, an instability that is likely to be created by convectively driven vortices, occurring where the loop field intersects the photosphere (i.e. the loop footpoints). The large-scale deformation of the field caused by the kinking creates the conditions for the formation of strong current sheets and magnetic reconnection, which have previously been considered as sites of heating, under the assumption of an enhanced resistivity. However, our simulations indicate that slow mode shocks are the primary heating mechanism, since, as well as creating current sheets, magnetic reconnection also generates plasma flows that are faster than the slow magnetoacoustic wave speed.

scholarly journals ‘Ideally’ unstable current sheets and the triggering of fast magnetic reconnection

2016 ◽  
Vol 82 (5) ◽  
Author(s):  
A. Tenerani ◽  
M. Velli ◽  
F. Pucci ◽  
S. Landi ◽  
A. F. Rappazzo
Keyword(s):  
Magnetic Reconnection ◽  
Transient State ◽  
Quantitative Model ◽  
Two Dimensions ◽  
Dynamical Mechanism ◽  
Current Sheets ◽  
Tearing Instability ◽  
Kinetic Effects ◽  
Ratio Scales ◽  
Fast Reconnection

Magnetic reconnection is thought to be the dynamical mechanism underlying many explosive phenomena observed both in space and in the laboratory, although the question of how fast magnetic reconnection is triggered in such high Lundquist ($S$) number plasmas has remained elusive. It has been well established that reconnection can develop over time scales faster than those predicted traditionally once kinetic scales are reached. It has also been shown that, within the framework of resistive magnetohydrodynamics (MHD), fast reconnection is achieved for thin enough sheets via the onset of the so-called plasmoid instability. The latter was discovered in studies specifically devoted to the Sweet–Parker current sheet, either as an initial condition or an apparent transient state developing in nonlinear studies. On the other hand, a fast tearing instability can grow on an ideal, i.e. $S$-independent, time scale (dubbed ‘ideal’ tearing) within current sheets whose aspect ratio scales with the macroscopic Lundquist number as $L/a\sim S^{1/3}$ – much smaller than the Sweet–Parker one – suggesting a new way to approach to the initiation of fast reconnection in collapsing current configurations. Here we present an overview of what we have called ‘ideal’ tearing in resistive MHD, and discuss how the same reasoning can be extended to other plasma models commonly used that include electron inertia and kinetic effects. We then discuss a scenario for the onset of ‘ideal’ fast reconnection via collapsing current sheets and describe a quantitative model for the interpretation of the nonlinear evolution of ‘ideally’ unstable sheets in two dimensions.

scholarly journals How Turbulent is the Magnetically Closed Corona?

2021 ◽  
Vol 8 ◽  
Author(s):  
James A. Klimchuk ◽  
Spiro K. Antiochos
Keyword(s):  
Magnetic Reconnection ◽  
Large Scale ◽  
Direct Relationship ◽  
Spatial Scales ◽  
Complex Structure ◽  
Inertial Range ◽  
Small Current ◽  
Current Sheets ◽  
Energy Flows ◽  
Turbulent Cascade

We argue that the magnetically closed corona evolves primarily quasi-statically, punctuated by many localized bursts of activity associated with magnetic reconnection at a myriad of small current sheets. The sheets form by various processes that do not involve a traditional turbulent cascade whereby energy flows losslessly through a continuum of spatial scales starting from the large scale of the photospheric driving. If such an inertial range is a defining characteristic of turbulence, then the magnetically closed corona is not a turbulent system. It nonetheless has a complex structure that bears no direct relationship to the pattern of driving.

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