Force-Free Equilibria, Solar Flares and Coronal Transients

1979 ◽  
Vol 44 ◽  
pp. 174-178 ◽  
Author(s):  
J. Heyvaerts ◽  
J.M. Lasry ◽  
M. Schatzman ◽  
P. Witomsky
Keyword(s):  
Solar Flare ◽  
Solar Corona ◽  
Solar Flares ◽  
Magnetic Energy ◽  
Flare Phenomenon

The solar flare phenomenon is due to the sudden dissipation of magnetic energy in the solar corona. Growing evidence shows that flares may occur in closed magnetic configurations, and that photospheric shearing motions are essential in triggering the phenomenon. This prompted several authors (Lew, 1977; Jockers, 1977; Birn and Schindler, 1978, the present authors), to study the properties of magnetic configurations able to exist in the solar corona. Flares often occur in long “arcades of loops”, and this suggests as a first step a simplification of the problem by considering 2-dimensional structures

scholarly journals Solar and stellar flares and their impact on planets

2015 ◽  
Vol 11 (S320) ◽  
pp. 3-24
Author(s):  
Kazunari Shibata
Keyword(s):  
Solar Flare ◽  
Total Energy ◽  
Solar Flares ◽  
Magnetic Energy ◽  
Slow Rotation ◽  
The Sun ◽  
Stellar Flare ◽  
Terrestrial Environment ◽  
The Earth ◽  
Stellar Flares

AbstractRecent observations of the Sun revealed that the solar atmosphere is full of flares and flare-like phenomena, which affect terrestrial environment and our civilization. It has been established that flares are caused by the release of magnetic energy through magnetic reconnection. Many stars show flares similar to solar flares, and such stellar flares especially in stars with fast rotation are much more energetic than solar flares. These are called superflares. The total energy of a solar flare is 1029 − 1032 erg, while that of a superflare is 1033 − 1038 erg. Recently, it was found that superflares (with 1034 − 1035 erg) occur on Sun-like stars with slow rotation with frequency once in 800 - 5000 years. This suggests the possibility of superflares on the Sun. We review recent development of solar and stellar flare research, and briefly discuss possible impacts of superflares on the Earth and exoplanets.

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.

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>

Magnetic Energy Release and Transients in the Solar Flare of 2000 July 14

2001 ◽  
Vol 550 (1) ◽  
pp. L105-L108 ◽  
Author(s):  
A. G. Kosovichev ◽  
V. V. Zharkova
Keyword(s):  
Solar Flare ◽  
Energy Release ◽  
Magnetic Energy ◽  
Magnetic Energy Release

CHOICE OF CONDITIONS FOR MHD SIMULATIONS ABOVE THE ACTIVE REGION, ALLOWING THE STUDY OF THE SOLAR FLARE MECHANISM

2021 ◽  
Vol 44 ◽  
pp. 92-95
Author(s):  
A.I. Podgorny ◽  
◽  
I.M. Podgorny ◽  
A.V. Borisenko ◽  
N.S. Meshalkina ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Active Region ◽  
Solar Flare ◽  
Magnetic Energy ◽  
Solar Radius ◽  
Computational Domain ◽  
Mhd Simulations ◽  
Flare Energy ◽  
Numerical Instabilities ◽  
The Magnetic Field

Primordial release of solar flare energy high in corona (at altitudes 1/40 - 1/20 of the solar radius) is explained by release of the magnetic energy of the current sheet. The observed manifestations of the flare are explained by the electrodynamical model of a solar flare proposed by I. M. Podgorny. To study the flare mechanism is necessary to perform MHD simulations above a real active region (AR). MHD simulation in the solar corona in the real scale of time can only be carried out thanks to parallel calculations using CUDA technology. Methods have been developed for stabilizing numerical instabilities that arise near the boundary of the computational domain. Methods are applicable for low viscosities in the main part of the domain, for which the flare energy is effectively accumulated near the singularities of the magnetic field. Singular lines of the magnetic field, near which the field can have a rather complex configuration, coincide or are located near the observed positions of the flare.

Plasma Diagnostics of Microflares observed by STIX and AIA

2021 ◽  
Author(s):  
Jonas Saqri ◽  
Astrid Veronig ◽  
Ewan Dickson ◽  
Säm Krucker ◽  
Andrea Francesco Battaglia ◽  
...  
Keyword(s):  
Solar Flares ◽  
Magnetic Energy ◽  
Emission Measure ◽  
Transport Processes ◽  
X Rays ◽  
Solar Dynamics Observatory ◽  
Energy Bands ◽  
Accurate Analysis ◽  
Great Opportunity ◽  
Wide Range

<p>Solar flares are generally thought to be the impulsive release of magnetic energy giving rise to a wide range of solar phenomena that influence the heliosphere and in some cases even conditions of earth. Part of this liberated energy is used for particle acceleration and to heat up the solar plasma. The Spectrometer/Telescope for Imaging X-rays (STIX) instrument onboard the Solar Orbiter mission launched on February 10th 2020 promises advances in the study of solar flares of various sizes. It is capable of measuring X-ray spectra from 4 to 150 keV with 1 keV resolution binned into 32 energy bins before downlinking. With this energy range and sensitivity, STIX is capable of sampling thermal plasma with temperatures of≳10 MK, and to diagnose the nonthermal bremsstrahlung emission of flare-accelerated electrons. During the spacecraft commissioning phase in the first half of the year 2020, STIX observed 68 microflares. Of this set, 26 events could clearly be identified in at least two energy channels, all of which originated in an active region that was also visible from earth. These events provided a great opportunity to combine the STIX observations with the multi-band EUV imagery from the Atmospheric Imaging Assembly (AIA) instrument on board the earth orbiting Solar Dynamics Observatory (SDO). For the microflares that could be identified in two STIX science energy bands, it was possible to derive the temperature and emission measure (EM) of the flaring plasma assuming an isothermal source. For larger events where more detailed spectra could be derived, a more accurate analysis was performed by fitting the spectra assuming various thermal and nonthermal sources. These results are compared to the diagnostics derived from AIA images. To this aim, the Differential EmissionMeasure (DEM) was reconstructed from AIA observations to infer plasma temperatures and EM in the flaring regions. Combined with the the relative timing between the emission seen by STIX and AIA, this allows us to get deeper insight into the flare energy release and transport processes.</p>

scholarly journals On the Possibility of Local Magnetic Field Intensification in Evaporating Chromospheric Solar Flare Plasma

1989 ◽  
Vol 104 (2) ◽  
pp. 341-344
Author(s):  
V. N. Dermendjiev ◽  
G. T. Buyukliev ◽  
I. Ph. Panayotova
Keyword(s):  
Magnetic Field ◽  
Solar Flare ◽  
Solar Flares ◽  
Local Magnetic Field ◽  
Plume Structure ◽  
The Subject ◽  
Convective Plume ◽  
Flare Plasma ◽  
Initial Magnetic Field ◽  
Moving Vortex

The investigations of plasma motions at the initial phases of solar flares (Antonucci and Dennis, 1983; Doschek, 1983; Watanabe, 1987) suggest evaporation from the chromospheric flaring area. According to de Jager (1983) when seen at the limb the evaporated plasma will look like a “convective plume” and it can be seen separated from heated footpoint areas.The subject of this work is the study of the possibility of forming hydrodynamic structures o-f thermal and starting plume's kind at the time of evaporation of the upper chromosphere in a flaring area. Also the possibility of increasing an initial magnetic field by a periodically moving vortex in a plume structure is investigated.

scholarly journals MHD Aspects of Coronal Transients

1980 ◽  
Vol 91 ◽  
pp. 263-277 ◽  
Author(s):  
U. Anzer
Keyword(s):  
Solar Corona ◽  
Time Scales ◽  
White Light ◽  
Solar Flares ◽  
Great Length ◽  
X Ray

If one defines coronal transients as events which occur in the solar corona on rapid time scales (≲ several hours) then one would have to include a large variety of solar phenomena: flares, sprays, erupting prominences, X-ray transients, white light transients, etc. Here we shall focus our attention on the latter two phenomena; solar flares have been discussed at great length in a recent Skylab workshop and IAU Colloqium No. 44 was devoted to the study of prominences. Coronal transients, in the narrower sense, were first seen with the instruments on board of Skylab, both in the optical and the X-ray part of the spectrum.

scholarly journals Preface

1991 ◽  
Vol 336 (1643) ◽  
pp. 323-323
Keyword(s):  
Solar Flare ◽  
Energy Release ◽  
Gamma Rays ◽  
Solar Flares ◽  
Solar Maximum ◽  
Interplanetary Space ◽  
Release Site ◽  
Solar Maximum Mission ◽  
New Information ◽  
Three Space

During the period of the 1980 solar maximum three space missions (P78-1, Solar Maximum Mission and Hinotori ) carried out extensive studies of solar flares. In their different ways all of these missions contributed significant new information to our understanding of the solar flare phenomenon. In this volume the contribution made by these three spacecraft to the study of the energy release and the related creation of high-tem perature plasma, the transport of energy from the primary release site, the production of gamma-rays at energies up to 10 MeV and the ejection of solar matter into interplanetary space are reviewed.

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