The Role of Turbulence for Heating Plasmas in Eruptive Solar Flares

AbstractThis article focuses on two problems involved in the development of models of solar flares. The first concerns the mechanism responsible for eruptions, such as erupting filaments or coronal mass ejections, that are sometimes involved in the flare process. The concept of ‘loss of equilibrium’ is considered and it is argued that the concept typically arises in thought-experiments that do not represent acceptable physical behavior of the solar atmosphere. It is proposed instead that such eruptions are probably caused by an instability of a plasma configuration. The instability may be purely MHD, or it may combine both MHD and resistive processes. The second problem concerns the mechanism of energy release of the impulsive (or gradual) phase. It is proposed that this phase of flares may be due to current interruption, as was originally proposed by Alfvén and Carlqvist. However, in order for this process to be viable, it seems necessary to change one's ideas about the heating and structure of the corona in ways that are outlined briefly.

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The Role of Magnetic Helicity in Solar Flares

Highlights of Astronomy ◽

10.1017/s1539299600015318 ◽

2005 ◽

Vol 13 ◽

pp. 128-131

Author(s):

Mark G. Linton

Keyword(s):

Solar Flares ◽

Magnetic Energy ◽

Active Regions ◽

Excess Energy ◽

Flux Tubes ◽

Surplus Energy ◽

Coronal Magnetic Fields ◽

Kink Instability ◽

Magnetic Energy Release

AbstractHelicity in coronal magnetic fields, often occurring in the form of twisted or sheared fields, can provide surplus energy which is available for release in solar flares. In this paper, several models of how this extra, non-potential, energy can be released will be reviewed. For example, twisted flux tubes can release excess energy via the kink instability. Or energy can be released via a transfer of helicity between different magnetic tubes. For untwisted field, the mutual helicity between flux tubes provides a measure of the shear in the fields, and therefore how much energy is available for release in a flare. For twisted flux tubes, the twist helicity of each tube in combination with the mutual helicity between the tubes dictate what type of reconnection the tubes can undergo and how much energy is available for release. Measuring the helicity of coronal active regions, and studying how this helicity affects magnetic energy release is therefore vital for our understanding of and our ability to predict solar flares.

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Solar flare forecasting model using 3D magnetic field data

10.5194/egusphere-egu2020-13298 ◽

2020 ◽

Author(s):

Xin Huang

Keyword(s):

Magnetic Field ◽

Deep Learning ◽

Solar Flare ◽

Solar Flares ◽

Field Data ◽

Active Regions ◽

Forecasting Model ◽

Magnetic Field Data ◽

The Magnetic Field

<p>Solar flares originate from the release of the energy stored in the magnetic field of solar active regions. Generally, the photospheric magnetograms of active regions are used as the input of the solar flare forecasting model. However, solar flares are considered to occur in the low corona. Therefore, the role of 3D magnetic field of active regions in the solar flare forecast should be explored. We extrapolate the 3D magnetic field using the potential model for all the active regions during 2010 to 2017, and then the deep learning method is applied to extract the precursors of solar flares in the 3D magnetic field data. We find that the 3D magnetic field of active regions is helpful to build a deep learning based forecasting model.</p>

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The role of plasma ejections in the development of large solar flares of various durations

Astronomy Reports ◽

10.1134/s1063772906120067 ◽

2006 ◽

Vol 50 (12) ◽

pp. 1013-1025 ◽

Cited By ~ 6

Author(s):

A. N. Shakhovskaya ◽

M. A. Livshits ◽

I. M. Chertok

Keyword(s):

Solar Flares

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on the role of nonthermal electrons in EUV and X-ray line emissions from solar flares

Journal of Astrophysics and Astronomy ◽

10.1007/bf02714854 ◽

1997 ◽

Vol 18 (1) ◽

pp. 57-71 ◽

Cited By ~ 1

Author(s):

Ranjna Bakaya ◽

R. R. Rausaria

Keyword(s):

Solar Flares ◽

X Ray ◽

Nonthermal Electrons

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The role of protons in solar flares

Lecture Notes in Physics - Eruptive Solar Flares ◽

10.1007/3-540-55246-4_128 ◽

2008 ◽

pp. 363-366

Author(s):

D. Heristchi ◽

R. Boydr

Keyword(s):

Solar Flares

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Flare particle acceleration in the interaction of twisted coronal flux ropes

Astronomy and Astrophysics ◽

10.1051/0004-6361/201731915 ◽

2018 ◽

Vol 611 ◽

pp. A40 ◽

Cited By ~ 4

Author(s):

J. Threlfall ◽

A. W. Hood ◽

P. K. Browning

Keyword(s):

Particle Acceleration ◽

Solar Flares ◽

Three Dimensional ◽

Coronal Loops ◽

Mhd Simulation ◽

Mhd Simulations ◽

Uniform Background ◽

Energy Gains ◽

Particle Behaviour

Aim. The aim of this work is to investigate and characterise non-thermal particle behaviour in a three-dimensional (3D) magnetohydrodynamical (MHD) model of unstable multi-threaded flaring coronal loops.Methods. We have used a numerical scheme which solves the relativistic guiding centre approximation to study the motion of electrons and protons. The scheme uses snapshots from high resolution numerical MHD simulations of coronal loops containing two threads, where a single thread becomes unstable and (in one case) destabilises and merges with an additional thread.Results. The particle responses to the reconnection and fragmentation in MHD simulations of two loop threads are examined in detail. We illustrate the role played by uniform background resistivity and distinguish this from the role of anomalous resistivity using orbits in an MHD simulation where only one thread becomes unstable without destabilising further loop threads. We examine the (scalable) orbit energy gains and final positions recovered at different stages of a second MHD simulation wherein a secondary loop thread is destabilised by (and merges with) the first thread. We compare these results with other theoretical particle acceleration models in the context of observed energetic particle populations during solar flares.

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