Magnetic Reconnection and Particle Acceleration in Solar Flares

1998 ◽  
pp. 297-306 ◽  
Author(s):  
T. Kosugi ◽  
B. V. Somov
Keyword(s):  
Particle Acceleration ◽  
Magnetic Reconnection ◽  
Solar Flares

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>

Magnetic reconnection configurations and particle acceleration in solar flares

2007 ◽  
Vol 39 (9) ◽  
pp. 1421-1426 ◽  
Author(s):  
P.F. Chen ◽  
W.J. Liu ◽  
C. Fang
Keyword(s):  
Particle Acceleration ◽  
Magnetic Reconnection ◽  
Solar Flares

scholarly journals The solar system: a laboratory for the study of the physics of particle acceleration

2006 ◽  
Vol 2 (14) ◽  
pp. 83-85
Author(s):  
Robert P. Lin
Keyword(s):  
Particle Acceleration ◽  
Solar System ◽  
Magnetic Reconnection ◽  
Coronal Mass Ejections ◽  
Solar Flares ◽  
Electron Acceleration ◽  
Physical Conditions ◽  
System A ◽  
Bow Shocks ◽  
Imaging And Spectroscopy

AbstractA remarkable variety of particle acceleration occurs in the solar system, from lightning-related acceleration of electrons to tens of MeV energy in less than a millisecond in planetary atmospheres; to acceleration of auroral and radiation belt particles in planetary magnetospheres; to acceleration at planetary bow shocks, co-rotating interplanetary region shocks, shocks driven by fast coronal mass ejections, and possibly at the heliospheric termination shock; to acceleration in magnetic reconnection regions in solar flares and at planetary magnetopause and magnetotail current sheets. These acceleration processes often occur in conjunction with transient energy releases, and some are very efficient. Unlike acceleration processes outside the solar system, the accelerated particles and the physical conditions in the acceleration region can be studied through direct in situ measurements, and/or through detailed imaging and spectroscopy. Here I review recent observations of tens of MeV electron acceleration in the Earth's atmosphere and in the Earth's radiation belts, electron and ion acceleration related to magnetic reconnection in solar flares, electron acceleration to ≥ 300 keV in magnetic reconnection regions in the Earth's deep magnetotail, and acceleration of solar energetic particles (SEPs) by shocks driven by fast coronal mass ejections (CMEs).

scholarly journals Particle Acceleration Processes in the Solar Corona

1990 ◽  
Vol 43 (6) ◽  
pp. 703 ◽  
Author(s):  
DB Melrose
Keyword(s):  
Particle Acceleration ◽  
Magnetic Reconnection ◽  
Electric Fields ◽  
Solar Flares ◽  
Double Layers ◽  
Historical Outline ◽  
Diffusive Acceleration ◽  
Phase Acceleration ◽  
Resonant Acceleration ◽  
Shock Fronts

Theoretical ideas on particle acceleration associated with solar flares are reviewed. A historical outline is used to introduce the various acceleration mechanisms. These are stochastic acceleration in its various forms, diffusive acceleration at shock fronts, shock drift acceleration, resonant acceleration, acceleration during magnetic reconnection and acceleration by parallel electric fields in double layers or electrostatic shocks. Particular emphasis is placed on so-called first phase acceleration of electrons in solar flares, which is conventionally attributed to bulk energisation of electrons (Ramaty et al. 1980). There is no widely accepted theory for bulk energisation, which may be regarded as an enhanced form of heating. Ideas on bulk energisation are discussed critically. It is argued that the dissipation cannot be due to classical resistivity and involves anomalous resistivity or hyperresistivity, e.g., in multiple double layers. The dissipation must occur in very many localised regions. Bulk energisation due to magnetic reconnection is discussed briefly. A model for bulk energisation due to the continual formation and decay of weak double layers is outlined

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>

scholarly journals Double Coronal Hard and Soft X‐Ray Source Observed byRHESSI: Evidence for Magnetic Reconnection and Particle Acceleration in Solar Flares

2008 ◽  
Vol 676 (1) ◽  
pp. 704-716 ◽  
Author(s):  
Wei Liu ◽  
Vahé Petrosian ◽  
Brian R. Dennis ◽  
Yan Wei Jiang
Keyword(s):  
Particle Acceleration ◽  
Magnetic Reconnection ◽  
Solar Flares ◽  
X Ray

Magnetic reconnection in solar flares

2010 ◽  
Vol 180 (9) ◽  
pp. 997 ◽  
Author(s):  
B.V. Somov
Keyword(s):  
Magnetic Reconnection ◽  
Solar Flares

scholarly journals The effects of density inhomogeneities on the radio wave emission in electron beam plasmas

2021 ◽  
Vol 87 (2) ◽  
Author(s):  
Xin Yao ◽  
Patricio A. Muñoz ◽  
Jörg Büchner ◽  
Xiaowei Zhou ◽  
Siming Liu
Keyword(s):  
Magnetic Reconnection ◽  
Radio Wave ◽  
Solar Flares ◽  
Electron Beams ◽  
Distribution Functions ◽  
Plasma Emission ◽  
Langmuir Waves ◽  
Radio Emissions ◽  
Density Inhomogeneities ◽  
Effects Of Density

Type III radio bursts are radio emissions associated with solar flares. They are considered to be caused by electron beams travelling from the solar corona to the solar wind. Magnetic reconnection is a possible accelerator of electron beams in the course of solar flares since it causes unstable distribution functions and density inhomogeneities (cavities). The properties of radio emission by electron beams in an inhomogeneous environment are still poorly understood. We capture the nonlinear kinetic plasma processes of the generation of beam-related radio emissions in inhomogeneous plasmas by utilizing fully kinetic particle-in-cell code numerical simulations. Our model takes into account initial electron velocity distribution functions (EVDFs) as they are supposed to be created by magnetic reconnection. We focus our analysis on low-density regions with strong magnetic fields. The assumed EVDFs allow two distinct mechanisms of radio wave emissions: plasma emission due to wave–wave interactions and so-called electron cyclotron maser emission (ECME) due to direct wave–particle interactions. We investigate the effects of density inhomogeneities on the conversion of free energy from the electron beams into the energy of electrostatic and electromagnetic waves via plasma emission and ECME, as well as the frequency shift of electron resonances caused by perpendicular gradients in the beam EVDFs. Our most important finding is that the number of harmonics of Langmuir waves increases due to the presence of density inhomogeneities. The additional harmonics of Langmuir waves are generated by a coalescence of beam-generated Langmuir waves and their harmonics.

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