An Observational Overview of Solar Flares

Fletcher, L.; Dennis, B. R.; Hudson, H. S.; Krucker, S.; Phillips, K. J. H.; Veronig, Astrid; Battaglia, Marina; Bone, L.; Caspi, Amir; Chen, Q.; Gallagher, Peter T.; Grigis, P. C.; Ji, Haisheng; Liu, W.; Milligan, Ryan O.; Temmer, Manuela

doi:10.1007/s11214-010-9701-8

Cited by 701 publications

(461 citation statements)

References 451 publications

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“…Associate releases of mass and/or energy are called flares, eruptive prominences and CMEs, depending on the emission and dynamics observed (for reviews see, Benz 2008; Fletcher et al 2011;Mackay et al 2010;Parenti 2014;Hudson et al 2006;Webb and Howard 2012). Flares involve sudden enhancements of electromagnetic radiation, caused by accelerated particles and excessive heating of the coronal plasma.…”

Section: Dynamic Evolution: Eruptive Phenomenamentioning

confidence: 99%

The magnetic field in the solar atmosphere

Wiegelmann

Thalmann

Solanki

2014

Astron Astrophys Rev

176

125

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This publication provides an overview of magnetic fields in the solar atmosphere with the focus lying on the corona. The solar magnetic field couples the solar interior with the visible surface of the Sun and with its atmosphere. It is also responsible for all solar activity in its numerous manifestations. Thus, dynamic phenomena such as coronal mass ejections and flares are magnetically driven. In addition, the field also plays a crucial role in heating the solar chromosphere and corona as well as in accelerating the solar wind. Our main emphasis is the magnetic field in the upper solar atmosphere so that photospheric and chromospheric magnetic structures are mainly discussed where relevant for higher solar layers. Also, the discussion of the solar atmosphere and activity is limited to those topics of direct relevance to the magnetic field. After giving a brief overview about the solar magnetic field in general and its global structure, we discuss in more detail the magnetic field in active regions, the quiet Sun and coronal holes.

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Section: Dynamic Evolution: Eruptive Phenomenamentioning

confidence: 99%

The magnetic field in the solar atmosphere

Wiegelmann

Thalmann

Solanki

2014

Astron Astrophys Rev

176

125

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“…More details about solar flares can be found in several reviews (e.g. Hudson 2007;Benz 2008;Shibata & Magara 2011;Fletcher et al 2011).…”

Section: Introductionmentioning

confidence: 99%

Hαspectroscopy and multiwavelength imaging of a solar flare caused by filament eruption

Huang

Madjarska²,

Koleva

et al. 2014

A&A

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Context. We study a sequence of eruptive events including filament eruption, a GOES C4.3 flare, and a coronal mass ejection. Aims. We aim to identify the possible trigger(s) and precursor(s) of the filament destabilisation, investigate flare kernel characteristics, flare ribbons/kernels formation and evolution, study the interrelation of the filament-eruption/flare/coronal-mass-ejection phenomena as part of the integral active-region magnetic field configuration, and determine Hα line profile evolution during the eruptive phenomena. Methods. Multi-instrument observations are analysed including Hα line profiles, speckle images at Hα -0.8 Å and Hα + 0.8 Å from IBIS at DST/NSO, EUV images and magnetograms from the SDO, coronagraph images from STEREO, and the X-ray flux observations from Fermi and GOES. Results. We establish that the filament destabilisation and eruption are the main triggers for the flaring activity. A surge-like event with a circular ribbon in one of the filament footpoints is determined as the possible trigger of the filament destabilisation. Plasma draining in this footpoint is identified as the precursor for the filament eruption. A magnetic flux emergence prior to the filament destabilisation followed by a high rate of flux cancellation of 1.34 × 10 16 Mx s −1 is found during the flare activity. The flare X-ray lightcurves reveal three phases that are found to be associated with three different ribbons occurring consecutively. A kernel from each ribbon is selected and analysed. The kernel lightcurves and Hα line profiles reveal that the emission increase in the line centre is stronger than that in the line wings. A delay of around 5-6 min is found between the increase in the line centre and the occurrence of red asymmetry. Only red asymmetry is observed in the ribbons during the impulsive phases. Blue asymmetry is only associated with the dynamic filament.

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“…As a result, the emitting plasma trapped in coronal loops outlines the geometry of the magnetic field and their structural changes reflect the changes of the field connectivity (in general). Considerable pieces of evidence for features likely linked to reconnection in solar flares 7,8 and coronal mass ejections (CMEs 9 ) have been obtained so far. These include signatures of plasma inflow/outflow [10][11][12][13][14] , hot cusp structures 15 , current sheets [16][17][18] , fast-mode standing shocks 19 , and plasmoid ejection 20 .…”

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confidence: 99%

Imaging coronal magnetic-field reconnection in a solar flare

et al. 2013

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Abstract:Magnetic field reconnection is believed to play a fundamental role in magnetized plasma systems throughout the universe 1 , including planetary magnetospheres, magnetars, and accretion discs around black holes. This letter presents extreme ultraviolet (EUV) and X-ray observations of a solar flare showing magnetic reconnection with a level of clarity not previously achieved. The multi-wavelength EUV observations from SDO/AIA show inflowing cool loops and newly formed, outflowing hot loops, as predicted. RHESSI X-ray spectra and images simultaneously show the appearance of plasma heated to >10 MK at the expected locations. These two data sets provide solid visual evidence of magnetic reconnection producing a solar flare, validating the basic physical mechanism of popular flare models. However, new features are also observed that need to be included in reconnection and flare studies, such as 3D non-uniform, non-steady, and asymmetric evolution. Main Text:The early concept of magnetic reconnection was proposed in the 1940s 1 to explain energy release in solar flares, the most powerful explosive phenomena in the solar system. The reconnection process reconfigures the field topology and converts magnetic energy to thermal energy, mass motions, and particle acceleration. The theories and related numerical simulations, especially 3D modelling, are still subjects of extensive research to obtain a full understanding of the process under different conditions. Meanwhile, observational studies have made progress in finding evidence of reconnection and deriving its physical properties to constrain and improve the theories.In-situ measurements of the magnetic field, plasma parameters, and particle distributions have shown the existence of magnetic reconnection in laboratory plasmas 2, 3 , fusion facilities, and magnetospheres of planets 4,5 . Such in-situ measurements are still not possible in the extremely hot solar atmosphere. Instead, observations are obtained through remote sensing of emissions across the entire electromagnetic spectrum from radio to X rays and gamma rays.However, in the corona 6 the magnetic field pressure dominates the plasma pressure (low plasma beta) and the magnetic flux is "frozen into" the highly conductive plasma. As a result, the emitting plasma trapped in coronal loops outlines the geometry of the magnetic field and their structural changes reflect the changes of the field connectivity (in general). Considerable pieces of evidence for features likely linked to reconnection in solar flares 7,8 and coronal mass ejections (CMEs 9 ) have been obtained so far. These include signatures of plasma inflow/outflow 10-14 , hot cusp structures 15 , current sheets [16][17][18] , fast-mode standing shocks 19 , and plasmoid ejection 20 .However, most evidence has been indirect and fragmented. Detailed observations of the complete picture are still missing due to the highly dynamic flare/CME process and limited observational capabilities.The launch of the Solar Dynamic Observatory (SDO 21 ) in 2010 sign...

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An Observational Overview of Solar Flares

Cited by 701 publications

References 451 publications

The magnetic field in the solar atmosphere

The magnetic field in the solar atmosphere

Hαspectroscopy and multiwavelength imaging of a solar flare caused by filament eruption

Imaging coronal magnetic-field reconnection in a solar flare

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