scholarly journals The effect of a solar flare on chromospheric oscillations

2021 ◽  
Vol 503 (2) ◽  
pp. 2444-2456
Author(s):  
David C L Millar ◽  
Lyndsay Fletcher ◽  
Ryan O Milligan
Keyword(s):  
Solar Flares ◽  
Power Spectra ◽  
Active Regions ◽  
Impulsive Phase ◽  
Spectral Lines ◽  
Flare Activity ◽  
Imaging Data ◽  
Before And After ◽  
The Many ◽  
The Magnetic Field

ABSTRACT Oscillations in the solar atmosphere have long been observed both in quiet conditions and during solar flares. The chromosphere is known for its 3-min signals, which are strong over sunspot umbrae, and have periods determined by the chromosphere’s acoustic cut-off frequency. A small number of observations have shown the chromospheric signals to be affected by energetic events such as solar flares, however the link between flare activity and these oscillations remains unclear. In this work, we present evidence of changes to the oscillatory structure of the chromosphere over a sunspot which occurs during the impulsive phase of an M1 flare. Using imaging data from the CRISP instrument across the H α and Ca ii 8542  Å spectral lines, we employed a method of fitting models to power spectra to produce maps of where there is evidence of oscillatory signals above a red-noise background. Comparing results taken before and after the impulsive phase of the flare, we found that the oscillatory signals taken after the start of the flare differ in two ways: the locations of oscillatory signals had changed and the typical periods of the oscillations had tended to increase (in some cases increasing from <100 s to ∼200 s). Both of these results can be explained by a restructuring of the magnetic field in the chromosphere during the flare activity, which is backed up by images of coronal loops showing clear changes to magnetic connectivity. These results represent one of the many ways that active regions can be affected by solar flares.

Solar flare forecasting model using 3D magnetic field data

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>

scholarly journals Flows, Evolution of Magnetic Fields, and Flares

1993 ◽  
Vol 141 ◽  
pp. 323-332 ◽  
Author(s):  
Haimin Wang
Keyword(s):  
Magnetic Fields ◽  
Magnetic Structure ◽  
Solar Flares ◽  
Active Regions ◽  
Magnetic Polarity ◽  
Flux Emergence ◽  
Electric Currents ◽  
Magnetic Shear ◽  
Before And After

AbstractThis paper reviews observations on the evolution of magnetic fields and flows in active regions which produce major flares. It includes the following topics: (1) Relationship between magnetic shear and flares; (2) Relationship between electric currents and flares; (3) Flows in active regions, particularly the emergence of new flux inside sheared penumbrae, and the mixed magnetic polarity nature of this kind of flux emergence; and (4) Changes of magnetic structure immediately before and after major solar flares; in particular, I will describe some recent findings that shear may increase after major flares.

scholarly journals Magnetic Instabilities in Stellar Atmospheres

1983 ◽  
Vol 71 ◽  
pp. 545-558
Author(s):  
E.R. Priest
Keyword(s):  
Magnetic Field ◽  
Solar Flares ◽  
Impulsive Phase ◽  
Coronal Magnetic Field ◽  
Stellar Atmospheres ◽  
Stored Energy ◽  
Global Instability ◽  
Magnetohydrodynamic Instability ◽  
Kink Instability ◽  
The Magnetic Field

ABSTRACT.The extensive theory for magnetohydrodynamic instability of a flux tube is briefly reviewed, together with its application to tokamaks and solar flares. In a star a single coronal loop whose footprints are anchored in the dense photosphere may become unstable to the kink instability when it is twisted too much. Magnetic arcades may also be subject to an eruptive instability when they are sheared too much. After the eruption the magnetic field closes back down by reconnection and continues to heat the plasma long after the impulsive phase. Global instability of a large part of the coronal magnetic field is also possible when the stored energy is too great.

scholarly journals Machine learning reveals systematic accumulation of electric current in lead-up to solar flares

2019 ◽  
Vol 116 (23) ◽  
pp. 11141-11146 ◽  
Author(s):  
Dattaraj B. Dhuri ◽  
Shravan M. Hanasoge ◽  
Mark C. M. Cheung
Keyword(s):  
Magnetic Field ◽  
Machine Learning ◽  
Solar Flares ◽  
Active Regions ◽  
High Energy ◽  
Field Observations ◽  
High Energy Radiation ◽  
Before And After ◽  
Class Flare ◽  
Maxwell Stresses

Solar flares—bursts of high-energy radiation responsible for severe space weather effects—are a consequence of the occasional destabilization of magnetic fields rooted in active regions (ARs). The complexity of AR evolution is a barrier to a comprehensive understanding of flaring processes and accurate prediction. Although machine learning (ML) has been used to improve flare predictions, the potential for revealing precursors and associated physics has been underexploited. Here, we train ML algorithms to classify between vector–magnetic-field observations from flaring ARs, producing at least one M-/X-class flare, and nonflaring ARs. Analysis of magnetic-field observations accurately classified by the machine presents statistical evidence for (i) ARs persisting in flare-productive states—characterized by AR area—for days, before and after M- and X-class flare events; (ii) systematic preflare buildup of free energy in the form of electric currents, suggesting that the associated subsurface magnetic field is twisted; and (iii) intensification of Maxwell stresses in the corona above newly emerging ARs, days before first flares. These results provide insights into flare physics and improving flare forecasting.

scholarly journals A New Explanation for Flares on dMe Stars

1989 ◽  
Vol 104 (2) ◽  
pp. 357-360
Author(s):  
G.M. Simnett
Keyword(s):  
Magnetic Field ◽  
Energy Transfer ◽  
Solar Corona ◽  
Solar Flares ◽  
Active Regions ◽  
Strong Fields ◽  
Stellar Flares ◽  
Self Consistent ◽  
The Magnetic Field

AbstractIt has been proposed that non-thermal ions dominate the energy transfer at the onset of solar flares. Here we examine this hypothesis in the context of flares on dMe stars. If the magnetic field in the stellar corona is significantly larger than that in the solar corona, and if strong fields in the photosphere, analagous to active regions, are absent, then a self-consistent explanation of stellar flares may be formulated.

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 Sunspot Proper Motion and Flare Frequency

1995 ◽  
Vol 151 ◽  
pp. 45-46
Author(s):  
G. Csepura ◽  
L. Győri ◽  
A.A. Galal
Keyword(s):  
Magnetic Field ◽  
Active Region ◽  
Proper Motion ◽  
Active Regions ◽  
Field Configuration ◽  
Flare Activity ◽  
Magnetic Field Configuration ◽  
Spot Group ◽  
The Magnetic Field ◽  
Flare Frequency

Flare activity of solar active regions is generally believed to depend on a sheared configuration of magnetic fields (Hagyard et al. 1984). There are cases when the shear necessary for a flare can be attributed to the emergence of a new flux in the spot group (Wang 1992). But, perhaps, a newly born active region can also influence the magnetic field configuration in a nearby active region (Poleto et al. 1993, Gesztelyi et al. 1993). In this paper we are interested primarily in the influence of a newly emerging spot group on a nearby one.The three neighbouring active regions NOAA AR 6412(B-C), 6413(A) and 6415(D) have been studied between 13-22 December 1990. White-light pictures for studying sunspot proper motion and area evolution were taken at Gyula Observing Station (Hungary), Debrecen Heliophysical Observatory (Hungary) and Helwan Observatory (Egypt). Times and positions of the flares were taken from the Solar Geophysical Data (No. 558, part 1, February 1991).

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.

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