scholarly journals Observational Signatures of Tearing Instability in the Current Sheet of a Solar Flare

2022 ◽  
Vol 924 (1) ◽  
pp. L7
Author(s):  
Lei Lu ◽  
Li Feng ◽  
Alexander Warmuth ◽  
Astrid M. Veronig ◽  
Jing Huang ◽  
...  
Keyword(s):  
Solar Flare ◽  
Magnetic Reconnection ◽  
Current Sheet ◽  
Extreme Ultraviolet ◽  
Magnetic Energy ◽  
Plasma Heating ◽  
Particle Energy ◽  
Transport Processes ◽  
Data Set ◽  
Plasma Energy

Abstract Magnetic reconnection is a fundamental physical process converting magnetic energy into not only plasma energy but also particle energy in various astrophysical phenomena. In this Letter, we show a unique data set of a solar flare where various plasmoids were formed by a continually stretched current sheet. Extreme ultraviolet images captured reconnection inflows, outflows, and particularly the recurring plasma blobs (plasmoids). X-ray images reveal nonthermal emission sources at the lower end of the current sheet, presumably as large plasmoids with a sufficiently amount of energetic electrons trapped in them. In the radio domain, an upward, slowly drifting pulsation structure, followed by a rare pair of oppositely drifting structures, was observed. These structures are supposed to map the evolution of the primary and the secondary plasmoids formed in the current sheet. Our results on plasmoids at different locations and scales shed important light on the dynamics, plasma heating, particle acceleration, and transport processes in the turbulent current sheet and provide observational evidence for the cascading magnetic reconnection process.

Solar Flares

2020 ◽  
Author(s):  
Dana Longcope
Keyword(s):  
Solar Flare ◽  
Current Sheet ◽  
Extreme Ultraviolet ◽  
Magnetic Energy ◽  
Theoretical Models ◽  
Heat Radiation ◽  
Electromagnetic Spectrum ◽  
Model Framework ◽  
X Ray ◽  
Solar Brightness

A solar flare is a transient increase in solar brightness powered by the release of magnetic energy stored in the Sun’s corona. Flares are observed in all wavelengths of the electromagnetic spectrum. The released magnetic energy heats coronal plasma to temperatures exceeding ten million Kelvins, leading to a significant increase in solar brightness at X-ray and extreme ultraviolet wavelengths. The Sun’s overall brightness is normally low at these wavelengths, and a flare can increase it by two or more an orders of magnitude. The size of a given flare is traditionally characterized by its peak brightness in a soft X-ray wavelength. Flares occur with frequency inversely related to this measure of size, with those of greatest size occuring less than once per year. Images and light curves from different parts of the spectrum from many different flares have led to an accepted model framework for explaining the typical solar flare. According to this model, a sheet of electric current (a current sheet) is first formed in the corona, perhaps by a coronal mass ejection. Magnetic reconnection at this current sheet allows stored magnetic energy to be converted into bulk flow energy, heat, radiation, and a population of non-thermal electrons and ions. Some of this energy is transmitted downward to cooler layers, which are then evaporated (or ablated) upward to fill the coronal with hot dense plasma. Much of the flares bright emission comes from this newly heated plasma. Theoretical models have been proposed to describe each step in this process.

Energetic electron acceleration during magnetic reconnection

2020 ◽  
Author(s):  
Huishan Fu
Keyword(s):  
Numerical Simulations ◽  
Magnetic Reconnection ◽  
Magnetic Energy ◽  
Energetic Electron ◽  
Electron Acceleration ◽  
Particle Energy ◽  
Acceleration Process ◽  
The Earth

<p>During magnetic reconnection, magnetic energy is explosively converted to particle energy and consequently electrons are accelerated to hundreds of keV that are dangerous to spacecraft and astronauts. To date, how and where the acceleration happens during reconnection is still unknown. Also, how efficient can the acceleration be remains a puzzle. Using spacecraft measurements (e.g., Cluster and MMS) and numerical simulations, many attempts have been made to answer these questions during the last twenty years. In this talk, I will briefly review these progresses and then show our recent results in understanding these issues. Specifically, I will (1) report a super-efficient electron acceleration by magnetic reconnection in the Earth’s magnetotail, during which electron fluxes are enhanced by 10000 times within 30 seconds; (2) discuss the mechanisms leading to super-efficient electron acceleration; (3) report the first evidence of electron acceleration at a reconnecting magnetopause, during which the acceleration process is nonadiabatic; and (4) report electron acceleration in the </p>

scholarly journals Large solar-type magnetic reconnection model for magnetar giant flare

2008 ◽  
Vol 4 (S259) ◽  
pp. 123-124
Author(s):  
Youhei Masada
Keyword(s):  
Solar Flare ◽  
Magnetic Reconnection ◽  
Radiative Heat ◽  
Energy Transport ◽  
Magnetic Energy ◽  
Baryonic Matter ◽  
Solar Type ◽  
Mass Ejection ◽  
Giant Flare ◽  
Reconnection Model

AbstractWe construct a magnetic reconnection model for magnetar giant flare in the framework of solar flare/coronal mass ejection theory. As is the case with the solar flare, the explosive magnetic reconnection plays a crucial role in the energetics of the magnetar flare. A key physics controlling the energy transport in the system, on the other hand, is the radiative process unlike that in the solar flare. After the release of the magnetic energy via the magnetic reconnection, the radiative heat flux drives the baryonic evaporation. Our model can predict that the baryonic matter evaporated in the preflare stage would be the origin of the radio emitting ejecta observed in association with the giant flare on 2004 December 27 from SGR1806-20.

scholarly journals Magnetic-field annihilation and island formation in electron-scale current sheet in Earth's magnetotail

2020 ◽  
Author(s):  
Hiroshi Hasegawa ◽  
Richard Denton ◽  
Kevin Genestreti ◽  
Takuma Nakamura ◽  
Tai Phan ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Energy Conversion ◽  
Current Sheet ◽  
Magnetic Energy ◽  
Particle Energy ◽  
Planar Geometry ◽  
Diffusion Region ◽  
Magnetospheric Substorms ◽  
Flow Energy ◽  
The Impact

Abstract Establishing the mechanism of magnetic-to-particle energy conversion through magnetic reconnection in current sheets1 is the key to understanding the impact of fast release of magnetic energy in many space and astrophysical plasma systems, such as during magnetospheric substorms2,3. It is generally believed that an electron-scale diffusion region (EDR), where a magnetic-to-electron energy conversion occurs, has an X-type magnetic-field geometry4 around which the energy of anti-parallel magnetic fields injected is mostly converted to the bulk-flow energy of electrons by magnetic tension of reconnected field-lines5,6. However, it is at present unknown exactly how this energy conversion occurs in EDRs, because there has been no observational method to fully address this problem. Here we present state-of-the-art analysis of multi-spacecraft observations in Earth’s magnetotail of an electron-scale current sheet, which demonstrates that contrary to the standard model of reconnection with an X-type EDR geometry, the fast energy conversion in the detected EDR was caused mostly by magnetic-field annihilation, rather than reconnection. Furthermore, we detected a magnetic island forming in the EDR itself, implying that the EDR had an elongated shape ideal for island generation7 and magnetic-field annihilation. The experimental discovery of the annihilation-dominated EDR reveals a new form of energy conversion in the reconnection process that can occur when the EDR has evolved from the X-type to planar geometry.

Hα, Extreme‐Ultraviolet, and Microwave Observations of the 2000 March 22 Solar Flare and Spontaneous Magnetic Reconnection

2003 ◽  
Vol 585 (1) ◽  
pp. 524-535 ◽  
Author(s):  
Jeongwoo Lee ◽  
Peter T. Gallagher ◽  
Dale E. Gary ◽  
Gelu M. Nita ◽  
G. S. Choe ◽  
...  
Keyword(s):  
Solar Flare ◽  
Magnetic Reconnection ◽  
Extreme Ultraviolet

scholarly journals Nature of the energy source powering solar coronal loops driven by nanoflares

2018 ◽  
Vol 615 ◽  
pp. L9 ◽  
Author(s):  
L. P. Chitta ◽  
H. Peter ◽  
S. K. Solanki
Keyword(s):  
Magnetic Field ◽  
Energy Source ◽  
Extreme Ultraviolet ◽  
Magnetic Energy ◽  
Plasma Heating ◽  
Active Regions ◽  
Coronal Loops ◽  
Solar Dynamics Observatory ◽  
Mixed Polarity ◽  
Solar Dynamics

Context. Magnetic energy is required to heat the corona, the outer atmosphere of the Sun, to millions of degrees. Aims. We study the nature of the magnetic energy source that is probably responsible for the brightening of coronal loops driven by nanoflares in the cores of solar active regions. Methods. We consider observations of two active regions (ARs), 11890 and 12234, in which nanoflares have been detected. To this end, we use ultraviolet (UV) and extreme ultraviolet (EUV) images from the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO) for coronal loop diagnostics. These images are combined with the co-temporal line-of-sight magnetic field maps from the Helioseismic and Magnetic Imager (HMI) onboard SDO to investigate the connection between coronal loops and their magnetic roots in the photosphere. Results. The core of these ARs exhibit loop brightening in multiple EUV channels of AIA, particularly in its 9.4 nm filter. The HMI magnetic field maps reveal the presence of a complex mixed polarity magnetic field distribution at the base of these loops. We detect the cancellation of photospheric magnetic flux at these locations at a rate of about 1015 Mx s−1. The associated compact coronal brightenings directly above the cancelling magnetic features are indicative of plasma heating due to chromospheric magnetic reconnection. Conclusions. We suggest that the complex magnetic topology and the evolution of magnetic field, such as flux cancellation in the photosphere and the resulting chromospheric reconnection, can play an important role in energizing active region coronal loops driven by nanoflares. Our estimate of magnetic energy release during flux cancellation in the quiet Sun suggests that chromospheric reconnection can also power the quiet corona.

Recent progress made in numerical experiments on magnetic reconnection and the related solar activities 

2021 ◽  
Author(s):  
Jun Lin ◽  
Jing Ye
Keyword(s):  
Magnetic Reconnection ◽  
Solar Flares ◽  
Numerical Experiments ◽  
Recent Progress ◽  
Magnetic Energy ◽  
Solar Physics ◽  
Plasma Heating ◽  
Mhd Turbulence ◽  
2D And 3D ◽  
Made In

<p>Magnetic reconnection plays a crucial role in the process of solar flares and coronal mass ejections, in which large amounts of magnetic energy (10^29-10^32 ergs) are converted into kinetic energy and thermal energy, even allowing for particle acceleration. On the platform of the Computational Solar Physics Laboratory of Yunnan Observatories, we have performed a series of numerical experiments on magnetic reconnection related to solar eruption events as well as numerical method developments both in 2D and 3D. In this talk, we will present some recent studies on the topic of plasma heating by reconnection, MHD turbulence, wave structures and complicate structures of CMEs, etc. Our numerical results have great potentials to explain and predict many related solar activities in the corona. </p>

Filamentary Currents in Turbulent Magnetic Reconnection

2020 ◽  
Author(s):  
Meng Zhou ◽  
Xiaohua Deng ◽  
Zhihong Zhong ◽  
Ye Pang
Keyword(s):  
Plasma Physics ◽  
Magnetic Reconnection ◽  
Current Sheet ◽  
Coherent Structures ◽  
High Speed ◽  
Large Scale ◽  
Magnetic Energy ◽  
Normal Direction ◽  
Neutral Sheet ◽  
Current Filaments

<p>Magnetic reconnection and turbulence are the two most important energy conversion phenomena in plasma physics. Magnetic reconnection and turbulence are often intertwined. For example, reconnection occurs in thin current layers formed during cascades of turbulence, while reconnection in large-scale current sheet also evolves into turbulence. How energy is dissipated and how particles are accelerated in turbulent magnetic reconnection are outstanding questions in magnetic reconnection and turbulence. Here we report MMS observations of filamentary currents in turbulent outflows in the Earth's magnetotail. We found sub-ion-scale filamentary currents in high-speed outflows that evolved into turbulent states. The normal direction of these current filaments is mainly along the X<sub>GSM</sub> direction, which is distinct from the neutral sheet. Some filamentary currents were reconnecting, thereby further dissipating the magnetic energy far from the X line. We notice that turbulent reconnection is more efficient in energizing electrons than laminar reconnection. Coherent structures composed of these filaments may be important in accelerating particles during turbulent reconnection.  </p>

scholarly journals Three-dimensional simulations of magnetic reconnection in a dusty plasma

2008 ◽  
Vol 74 (4) ◽  
pp. 493-513 ◽  
Author(s):  
SAMUEL A. LAZERSON ◽  
HEINZ M. WIECHEN
Keyword(s):  
Magnetic Reconnection ◽  
Current Sheet ◽  
Dusty Plasma ◽  
Aerodynamic Drag ◽  
Magnetic Energy ◽  
Three Dimensional ◽  
Dust Particles ◽  
Classical Models ◽  
Parameter Dependent ◽  
Three Dimensional Simulations

AbstractWe present the results of three-dimensional self-consistent multi-fluid simulations of magnetic reconnection in a dusty plasma. We ballistically relax a Harris-like current sheet into a fluid pseudo-equilibrium. We then perturb the current sheet with typical inflow and outflow velocities associated with classical models of reconnection. We find a 20% decrease in magnetic energy for the case of a locally enhanced resistivity. For a parameter-dependent resistivity we find a 26% decrease in magnetic energy in the current sheet. We find dust-neutral relative flow velocities that are a factor of two greater than the dust Alfvén velocity. We then explore the implications of these flows on aerodynamic drag heating of the dust particles.

scholarly journals Three-dimensional magnetic reconnection in astrophysical plasmas

2021 ◽  
Vol 477 (2249) ◽  
Author(s):  
Ting Li ◽  
Eric Priest ◽  
Ruilong Guo
Keyword(s):  
Magnetic Reconnection ◽  
Solar Flares ◽  
Magnetic Energy ◽  
Three Dimensional ◽  
Particle Energy ◽  
Two Dimensions ◽  
Three Dimensions ◽  
New Paradigm ◽  
Astrophysical Plasmas ◽  
Fundamental Process

Magnetic reconnection is a fundamental process in laboratory, magnetospheric, solar and astrophysical plasmas, whereby magnetic energy is converted into heat, bulk kinetic energy and fast particle energy. Its nature in two dimensions is much better understood than that in three dimensions, where its character is completely different and has many diverse aspects that are currently being explored. Here, we focus on the magnetohydrodynamics of three-dimensional reconnection in the plasma environment of the Solar System, especially solar flares. The theory of reconnection at null points, separators and quasi-separators is described, together with accounts of numerical simulations and observations of these three types of reconnection. The distinction between separator and quasi-separator reconnection is a theoretical one that is unimportant for the observations of energy release. A new paradigm for solar flares, in which three-dimensional reconnection plays a central role, is proposed.

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