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>

scholarly journals Astrophysical MHD turbulence: confluence of observations, simulations, and theory

2012 ◽  
Vol 8 (S294) ◽  
pp. 325-336 ◽  
Author(s):  
Blakesley Burkhart ◽  
Alex Lazarian
Keyword(s):  
Star Formation ◽  
Interstellar Medium ◽  
Magnetic Reconnection ◽  
Particle Transport ◽  
Recent Progress ◽  
Critical Component ◽  
Dynamo Theory ◽  
Mhd Turbulence ◽  
The Galaxy

AbstractMagnetohydrodynamic (MHD) turbulence is a critical component of the current paradigms of star formation, dynamo theory, particle transport, magnetic reconnection and evolution of the ISM. In order to gain understanding of how MHD turbulence regulates processes in the Galaxy, a confluence of numerics, observations and theory must be imployed. In these proceedings we review recent progress that has been made on the connections between theoretical, numerical, and observational understanding of MHD turbulence as it applies to both the neutral and ionized interstellar medium.

Large-scale particle acceleration during magnetic reconnection in solar flares

2020 ◽  
Author(s):  
Xiaocan Li ◽  
Fan Guo
Keyword(s):  
Particle Acceleration ◽  
Magnetic Reconnection ◽  
Power Law ◽  
Solar Flares ◽  
Large Scale ◽  
Magnetic Energy ◽  
High Energy ◽  
Macroscopic Model ◽  
Scale Particle ◽  
Reconnection Layer

<p>Magnetic reconnection is a primary driver of magnetic energy release and particle acceleration processes in space and astrophysical plasmas. Solar flares are a great example where observations have suggested that a large fraction of magnetic energy is converted into nonthermal particles and radiation. One of the major unsolved problems in reconnection studies is nonthermal particle acceleration. In the past decade or two, 2D kinetic simulations have been widely used and have identified several acceleration mechanisms in reconnection. Recent 3D simulations have shown that the reconnection layer naturally generates magnetic turbulence. Here we report our recent progresses in building a macroscopic model that includes these physics for explaining particle acceleration during solar flares. We show that, for sufficient large systems, high-energy particle acceleration processes can be well described as flow compression and shear. By means of 3D kinetic simulations, we found that the self-generated turbulence is essential for the formation of power-law electron energy spectrum in non-relativistic reconnection. Based on these results, we then proceed to solve an energetic particle transport equation in a compressible reconnection layer provided by high-Lundquist-number MHD simulations. Due to the compression effect, particles are accelerated to high energies and develop power-law energy distributions. The power-law index and maximum energy are both comparable to solar flare observations. This study clarifies the nature of particle acceleration in large-scale reconnection sites and initializes a framework for studying large-scale particle acceleration during solar flares.</p>

scholarly journals Three-dimensional magnetic reconnection and its application to solar flares

2017 ◽  
Vol 83 (1) ◽  
Author(s):  
Miho Janvier
Keyword(s):  
Kinetic Energy ◽  
Numerical Simulations ◽  
Magnetic Reconnection ◽  
Solar Flares ◽  
Magnetic Energy ◽  
Three Dimensional ◽  
Three Dimensions ◽  
Current Layer ◽  
Solar Observations ◽  
The Universe

Solar flares are powerful radiations occurring in the Sun’s atmosphere. They are powered by magnetic reconnection, a phenomenon that can convert magnetic energy into other forms of energy such as heat and kinetic energy, and which is believed to be ubiquitous in the universe. With the ever increasing spatial and temporal resolutions of solar observations, as well as numerical simulations benefiting from increasing computer power, we can now probe into the nature and the characteristics of magnetic reconnection in three dimensions to better understand the phenomenon’s consequences during eruptive flares in our star’s atmosphere. We review in the following the efforts made on different fronts to approach the problem of magnetic reconnection. In particular, we will see how understanding the magnetic topology in three dimensions helps in locating the most probable regions for reconnection to occur, how the current layer evolves in three dimensions and how reconnection leads to the formation of flux ropes, plasmoids and flaring loops.

Understanding the connection between the energy released during solar flares and their emission in the lower atmosphere

2016 ◽  
Vol 12 (S327) ◽  
pp. 94-102
Author(s):  
F. Rubio da Costa
Keyword(s):  
Solar Flares ◽  
Gamma Ray ◽  
Magnetic Energy ◽  
Solar Physics ◽  
Lower Atmosphere ◽  
Continuum Emission ◽  
Hydrodynamic Models ◽  
Flare Loop ◽  
Sudden Release ◽  
Explosive Events

AbstractWhile progress has been made on understanding how energy is released and deposited along the solar atmosphere during explosive events such as solar flares, the chromospheric and coronal heating through the sudden release of magnetic energy remain an open problem in solar physics. Recent hydrodynamic models allow to investigate the energy deposition along a flare loop and to study the response of the chromosphere. These results have been improved with the consideration of transport and acceleration of particles along the loop.RHESSIandFermi/GBM X-ray and gamma-ray observations help to constrain the spectral properties of the injected electrons. The excellent spatial, spectral and temporal resolution ofIRISwill also help us to constrain properties of explosive events, such as the continuum emission during flares or their emission in the chromosphere.

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.

scholarly journals Magnetic Reconnection: Phantom Theory

2020 ◽  
Vol 3 (2) ◽  
pp. p66
Author(s):  
Syun-Ichi Akasofu
Keyword(s):  
Global Warming ◽  
Magnetic Reconnection ◽  
Solar Flares ◽  
Solar Physics ◽  
Scientific Field ◽  
Half Century ◽  
Auroral Physics ◽  
Unusual Situation

In any scientific field, there is always a possibility, in which a particular theory dominates for many years. In this paper, the theory of magnetic reconnection in solar physics and auroral physics is reviewed as an example. It has prevailed for more than a half century in both fields as the “only one” without a concrete progress in understanding the source of energy for solar flares and auroral activities. This unusual situation is analyzed why and how it occurred. Since such a situation could occur in any scientific field, it may be useful to analyze how this situation happened. Actually, it is pointed out that a study of global warming may also be in a similar situation.

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.

scholarly journals Storing free magnetic energy in the solar corona

2016 ◽  
Vol 82 (4) ◽  
Author(s):  
G. Vekstein
Keyword(s):  
Solar Corona ◽  
Solar Flares ◽  
Magnetic Energy ◽  
Solar Physics ◽  
Interested Reader ◽  
Convective Flows ◽  
Free Magnetic Energy ◽  
Wide Readership ◽  
Magnetic Arcade

This article presents a mini-tutorial aimed at a wide readership not familiar with the field of solar plasma physics. The exposition is centred around the issue of excess/free magnetic energy stored in the solar corona. A general consideration is followed with a particular example of coronal magnetic arcade, where free magnetic energy builds up by photospheric convective flows. In the context of solar physics the major task is to explain how this free energy can be released quickly enough to match what is observed in coronal explosive events such as solar flares. Therefore, in the last section of the paper we discuss briefly a possible role of magnetic reconnection in these processes. This is done in quite simple qualitative physical terms, so that an interested reader can follow it up in more detail with help of the provided references.

The magnetohydrodynamics of energy release in solar flares

1991 ◽  
Vol 336 (1643) ◽  
pp. 363-380 ◽  
Keyword(s):  
Solar Flares ◽  
Numerical Experiments ◽  
Magnetic Energy ◽  
Numerical Models ◽  
Three Dimensions ◽  
Flare Loops ◽  
New Process ◽  
Field Lines ◽  
A Current ◽  
Magnetic Arcade

A large solar flare is thought to occur when a sheared magnetic arcade loses equilibrium or goes unstable and erupts, and drives magnetic re-connection in the stretched-out magnetic field lines. These two key processes of magnetic eruption and magnetic energy conversion by re-connection are reviewed briefly, with an account of recent analytical and numerical models. When the height or length of a prominence in a sheared coronal arcade is too great it may erupt and drive the formation and re-connection of a current sheet below it. Recent progress in fast steady-state re-connection theory has explained many puzzling features of numerical experiments, and has shown how a new process of magnetic flipping can reconnect fields in three dimensions. Also numerical modelling of the formation of flare loops and ribbons by re-connection has accounted for many observational properties.

Characterization of turbulent magnetic reconnection in solar flares with microwave imaging spectroscopy

2020 ◽  
Author(s):  
Gregory Fleishman ◽  
Dale Gary ◽  
Bin Chen ◽  
Sijie Yu ◽  
Natsuha Kuroda ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Particle Acceleration ◽  
Solar Flare ◽  
Magnetic Reconnection ◽  
Solar Flares ◽  
Magnetic Energy ◽  
Imaging Spectroscopy ◽  
Coronal Magnetic Field ◽  
Microwave Imaging ◽  
Cusp Region

<p>Magnetic reconnection plays a central role in highly magnetized plasma, for example, in solar corona. Release of magnetic energy due to reconnection is believed to drive such transient phenomena as solar flares, eruptions, and jets. This energy release should be associated with a decrease of the coronal magnetic field. Quantitative measurements of the evolving magnetic field strength in the corona are required to find out where exactly and with what rate this decrease takes place. The only available methodology capable of providing such measurements employs microwave imaging spectroscopy of gyrosynchrotron emission from nonthermal electrons accelerated in flares. Here, we report microwave observations of a solar flare, showing spatial and temporal changes in the coronal magnetic field at the cusp region; well below the nominal reconnection X point. The field decays at a rate of ~5 Gauss per second for 2 minutes. This fast rate of decay implies a highly enhanced, turbulent magnetic diffusivity and sufficiently strong electric field to account for the particle acceleration that produces the microwave emission. Moreover, spatially resolved maps of the nonthermal and thermal electron densities derived from the same microwave spectroscopy data set allow us to detect the very acceleration site located within the cusp region. The nonthermal number density is extremely high, while the thermal one is undetectably low in this region indicative of a bulk acceleration process exactly where the magnetic field displays the fast decay. The decrease in stored magnetic energy is sufficient to power the solar flare, including the associated eruption, particle acceleration, and plasma heating. We discuss implications of these findings for understanding particle acceleration in solar flares and in a broader space plasma context.</p>

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