Trigger mechanisms of the major solar flares

2019 ◽  
Vol 15 (S354) ◽  
pp. 392-406
Author(s):  
Shuhong Yang
Keyword(s):  
Active Region ◽  
Solar Flares ◽  
Magnetic Energy ◽  
Active Regions ◽  
Polarity Inversion ◽  
Strong Gradient ◽  
Cycle 24 ◽  
Kink Instability ◽  
Shearing Motion ◽  
Trigger Mechanisms

AbstractSolar flares, suddenly releasing a large amount of magnetic energy, are one of the most energetic phenomena on the Sun. For the major flares (M- and X-class flares), there exist strong-gradient polarity-inversion lines in the pre-flare photospheric magnetograms. Some parameters (e.g., electric current, shear angle, free energy) are used to measure the magnetic non-potentiality of active regions, and the kernels of major flares coincide with the highly non-potential regions. Magnetic flux emergence and cancellation, shearing motion, and sunspot rotation observed in the photosphere are deemed to play an important role in the energy buildup and flare trigger. Solar active region 12673 produced many major flares, among which the X9.3 flare is the largest one in solar cycle 24. According to the newly proposed block-induced eruption model, the block-induced complex structures built the flare-productive active region and the X9.3 flare was triggered by an erupting filament due to the kink instability.

scholarly journals The Role of Magnetic Helicity in Solar Flares

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.

scholarly journals Evolution of the Active Region NOAA 12443 based on magnetic field extrapolations: preliminary results

2016 ◽  
Vol 12 (S328) ◽  
pp. 127-129
Author(s):  
André Chicrala ◽  
Renato Sergio Dallaqua ◽  
Luis Eduardo Antunes Vieira ◽  
Alisson Dal Lago ◽  
Jenny Marcela Rodríguez Gómez ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Active Region ◽  
Magnetic Structure ◽  
Solar Flares ◽  
Solar Surface ◽  
Magnetic Energy ◽  
Active Regions ◽  
X Ray ◽  
Surface Magnetic Field ◽  
The Magnetic Field

AbstractThe behavior of Active Regions (ARs) is directly related to the occurrence of some remarkable phenomena in the Sun such as solar flares or coronal mass ejections (CME). In this sense, changes in the magnetic field of the region can be used to uncover other relevant features like the evolution of the ARs magnetic structure and the plasma flow related to it. In this work we describe the evolution of the magnetic structure of the active region AR NOAA12443 observed from 2015/10/30 to 2015/11/10, which may be associated with several X-ray flares of classes C and M. The analysis is based on observations of the solar surface and atmosphere provided by HMI and AIA instruments on board of the SDO spacecraft. In order to investigate the magnetic energy buildup and release of the ARs, we shall employ potential and linear force free extrapolations based on the solar surface magnetic field distribution and the photospheric velocity fields.

scholarly journals The Evolution of Unstable 'Beta-Gamma' Magnetic Fields of Active Region AR 2222

2015 ◽  
Vol 48 ◽  
pp. 95-102
Author(s):  
Zety Sharizat Hamidi ◽  
S.N.U. Sabri ◽  
N.N.M. Shariff ◽  
C. Monstein
Keyword(s):  
Active Region ◽  
Magnetic Fields ◽  
Solar Corona ◽  
Solar Flares ◽  
Active Regions ◽  
Group Type ◽  
Solar Burst ◽  
Type Iv ◽  
Fine Structures ◽  
Using Data

This event allows us to investigate how plasma–magnetic field interactions in the solar corona can produce suprathermal electron populations over periods from tens of minutes to several hours, and the interactions of wave-particle and wave-wave lead to characteristic fine structures of the emission. An intense and broad solar radio burst type IV was recorded by CALLISTO spectrometer from 240-360 MHz. Using data from a the KRIM observatory, we aim to provide a comprehensive description of the synopsis formation and dynamics of a a single solar burst type IV event due to active region AR2222. For five minutes, the event exhibited strong pulsations on various time scales and “broad patterns” with a formation of a group type III solar burst. AR 2222 remained the most active region, producing a number of minor C-Class solar flares. The speed of the solar wind also exceeds 370.8 km/second with 10.2 g/cm3 density of proton in the solar corona. The radio flux also shows 171 SFU. Besides, there are 3 active regions, AR2217, AR2219 and AR2222 potentially pose a threat for M-class solar flares. Active region AR2222 have unstable 'beta-gamma' magnetic fields that harbor energy for M-class flares. As a conclusion, we believed that Sun’s activities more active in order to achieve solar maximum cycle at the end of 2014.

A physics-based method that can predict imminent large solar flares

Science ◽  
2020 ◽  
Vol 369 (6503) ◽  
pp. 587-591 ◽  
Author(s):  
Kanya Kusano ◽  
Tomoya Iju ◽  
Yumi Bamba ◽  
Satoshi Inoue
Keyword(s):  
Solar Cycle ◽  
Solar Flares ◽  
Solar Surface ◽  
Magnetic Polarity ◽  
Empirical Methods ◽  
Polarity Inversion ◽  
Solar Cycle 24 ◽  
Polarity Inversion Line ◽  
Magnetohydrodynamic Instability ◽  
Cycle 24

Solar flares are highly energetic events in the Sun’s corona that affect Earth’s space weather. The mechanism that drives the onset of solar flares is unknown, hampering efforts to forecast them, which mostly rely on empirical methods. We present the κ-scheme, a physics-based model to predict large solar flares through a critical condition of magnetohydrodynamic instability, triggered by magnetic reconnection. Analysis of the largest (X-class) flares from 2008 to 2019 (during solar cycle 24) shows that the κ-scheme predicts most imminent large solar flares, with a small number of exceptions for confined flares. We conclude that magnetic twist flux density, close to a magnetic polarity inversion line on the solar surface, determines when and where solar flares may occur and how large they can be.

scholarly journals Difference of source regions between fast and slow coronal mass ejections

2019 ◽  
Vol 36 ◽  
Author(s):  
B. Filippov
Keyword(s):  
Magnetic Field ◽  
Coronal Mass Ejections ◽  
Solar Flares ◽  
Magnetic Energy ◽  
Active Regions ◽  
Coronal Magnetic Field ◽  
Source Regions ◽  
Free Magnetic Energy ◽  
The Difference ◽  
Sunspot Groups

Abstract Coronal mass ejections (CMEs) are tightly related to filament eruptions and usually are their continuation in the upper solar corona. It is common practice to divide all observed CMEs into fast and slow ones. Fast CMEs usually follow eruptive events in active regions near big sunspot groups and associated with major solar flares. Slow CMEs are more related to eruptions of quiescent prominences located far from active regions. We analyse 10 eruptive events with particular attention to the events on 2013 September 29 and on 2016 January 26, one of which was associated with a fast CME, while another was followed by a slow CME. We estimated the initial store of free magnetic energy in the two regions and show the resemblance of pre-eruptive situations. The difference of late behaviour of the two eruptive prominences is a consequence of the different structure of magnetic field above the filaments. We estimated this structure on the basis of potential magnetic field calculations. Analysis of other eight events confirmed that all fast CMEs originate in regions with rapidly changing with height value and direction of coronal magnetic field.

Characteristics of Sunquake Events Observed in Solar Cycle 24

2021 ◽  
Author(s):  
Alexander Kosovichev ◽  
Ivan Sharykin
Keyword(s):  
Solar Cycle ◽  
Solar Flares ◽  
Active Regions ◽  
Impulsive Phase ◽  
High Energy ◽  
Lower Atmosphere ◽  
Solar Dynamics Observatory ◽  
X Ray ◽  
Solar Cycle 24 ◽  
Cycle 24

<p>Helioseismic response to solar flares ("sunquakes") occurs due to localized force or/and momentum impacts observed during the flare impulsive phase in the lower atmosphere. Such impacts may be caused by precipitation of high-energy particles, downward shocks, or magnetic Lorentz force. Understanding the mechanism of sunquakes is a key problem of the flare energy release and transport. Our statistical analysis of M-X class flares observed by the Solar Dynamics Observatory during Solar Cycle 24 has shown that contrary to expectations, many relatively weak M-class flares produced strong sunquakes, while for some powerful X-class flares, helioseismic waves were not observed or were weak. The analysis also revealed that there were active regions characterized by the most efficient generation of sunquakes during the solar cycle. We found that the sunquake power correlates with maximal values of the X-ray flux derivative better than with the X-ray class. The sunquake data challenge the current theories of solar flares.</p>

scholarly journals A Test to Confirm the Source of Energy for Solar Flares

2001 ◽  
Vol 18 (4) ◽  
pp. 351-354 ◽  
Author(s):  
M. S. Wheatland
Keyword(s):  
Active Region ◽  
Solar Flares ◽  
Large Scale ◽  
Virial Theorem ◽  
Magnetic Energy ◽  
Sufficient Data ◽  
Statistical Comparison ◽  
Independent Measure ◽  
Vector Magnetograms ◽  
Current Systems

AbstractA test of the hypothesis that flares derive their energy from large scale current systems inferred from active region vector magnetograms is proposed. The test involves a statistical comparison of the flarerelated change in coronal magnetic energy (based on the magnetohydrodynamic virial theorem) and an independent measure of the energy of the flare. A simulation suggests that — assuming the hypothesis is correct—the test requires around 50 flares with energy greater than 5×1023 J to return a significant result. Existing archives of vector magnetograms should provide sufficient data for such a study.

scholarly journals Searching for failed eruptions interacting with overlying magnetic field

2015 ◽  
Vol 11 (S320) ◽  
pp. 221-223 ◽  
Author(s):  
Dominik Gronkiewicz ◽  
Tomasz Mrozek ◽  
Sylwester Kołomański ◽  
Martyna Chruślińska
Keyword(s):  
Magnetic Field ◽  
Statistical Analysis ◽  
Active Region ◽  
Solar Flares ◽  
Active Regions ◽  
Automated Method ◽  
Solar Eruptions ◽  
Mass Ejection ◽  
The Magnetic Field ◽  
Flare Site

AbstractIt is well known that not all solar flares are connected with eruptions followed by coronal mass ejection (CME). Even strongest X-class flares may not be accompanied by eruptions or are accompanied by failed eruptions. One of important factor that prevent eruption from developing into CME is strength of the magnetic field overlying flare site. Few observations show that active regions with specific magnetic configuration may produce many CME-less solar flares. Therefore, forecasts of geoeffective events based on active region properties have to take into account probability of confining solar eruptions. Present observations of SDO/AIA give a chance for deep statistical analysis of properties of an active region which may lead to confining an eruption. We developed automated method which can recognize eruptions in AIA images. With this tool we will be able to analyze statistical properties of failed eruptions observed by AIA telescope.

Energy Balance and Structure Of Active Regions

1977 ◽  
Vol 36 ◽  
pp. 457-473 ◽  
Author(s):  
Frank Q. Orrall ◽  
Roger A. Kopp
Keyword(s):  
Solar Activity ◽  
Energy Balance ◽  
Active Region ◽  
Internal Structure ◽  
Solar Flares ◽  
Active Regions ◽  
Particle Emission ◽  
Space Astronomy ◽  
Coronal Bright Points ◽  
Definition Of

With the advent of radio and space astronomy it became necessary to extend the definition of a center of activity or active region (AR) originally proposed by L. d’Azambuja. At IAU Symposium 35, K.O. Klepenheuer (1968) defined an AR as “The totality of all observable phenomena preceding, accompanying and following the birth of sunspots, including radio-, X-, EUV-, and particle emission.” The recognition that there are other short-lived bipolar features with a distribution similar to that of active regions (ephemeral active regions) by Harveyet al. (1975) and their identification with coronal bright points by Golub et al. (1975) suggests that the definition will have to be extended further. Active regions manifest themselves in the photosphere as sunspots and faculae; in the chromosphere as the plage and its structures; in the corona as a coronal enhancement with a complex, often loop-like internal structure. (The termenhancementwas Introduced by Billings. The original termpermanent coronal condensation, introduced by Waldemeler, only referred to the very bright enhancements and was, moreover, often confused with hissporadic coronal condensations, a flareassodated phenomena. The termcoronal active regionhas, recently also been used for the coronal extension of the AR.) In keeping with the aims of this symposium the stress of this review will be on the chromosphere and corona. Active regions are especially Important as the site of most flare-associated phenomena. Here we shall be concerned with flares only as they affect the overall energy balance. Our concern is with the “quiet” active regions that cause the slowly varying components of solar activity and provide the ambiance within which solar flares occur.

Energetic electrons in solar flares: observational support for acceleration processes linked to magnetic reconnection

2021 ◽  
Author(s):  
Nicole Vilmer ◽  
Sophie Musset
Keyword(s):  
Solar Flares ◽  
Magnetic Energy ◽  
Imaging Spectroscopy ◽  
Active Regions ◽  
Coronal Magnetic Field ◽  
High Energy ◽  
X Rays ◽  
Energetic Electrons ◽  
Radio Imaging ◽  
Gyrosynchrotron Emission

<p>Efficient electron (and ion) acceleration is produced in association with solar flares. Energetic particles play a major role in the active Sun since they contain a large amount of the magnetic energy released during flares. Energetic electrons (and ions) interact with the solar atmosphere and produce high-energy X-rays and γ-rays. Energetic electrons also produce radio emission in a large frequency band through gyrosynchrotron emission processes in the magnetic fields of flaring active regions and conversion of plasma waves when e.g. propagating to the high corona towards the interplanetary medium. It is currently admitted that solar flares are powered by magnetic energy previously stored in the coronal magnetic field and that magnetic energy release is likely to occur on coronal currents sheets along regions of strong gradient of magnetic connectivity. However, understanding the connection between particle acceleration processes and the topology of the complex magnetic structures present in the corona is still a challenging issue. In this talk, we shall review some recent results derived from X-ray and radio imaging spectroscopy of solar flares bringing some new observational constraints on the localization of HXR/radio sources with respect to current sheets, termination shocks in the corona derived from EUV observations.</p>

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