Evolution of Photospheric Flow and Magnetic Fields Associated with the 2015 June 22 M6.5 Flare

Wang, Jiasheng; Liu, Chang; Deng, Na; Wang, Haimin

doi:10.3847/1538-4357/aaa712

Cited by 20 publications

(21 citation statements)

References 52 publications

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“…Vemareddy (2017) showed large shearing and converging motions in the following polarity sunspot before the flare. Rotational and shear flows are also found in both sides of the PIL during the flare (Bi et al 2017;Wang et al 2018). Figure 1(c) shows B z distribution taken at 16:36 UT.…”

Section: Observations and Numerical Methodsmentioning

confidence: 96%

Onset Mechanism of M6.5 Solar Flare Observed in Active Region 12371

Junsang¹,

Inoue²,

Kusano³

et al. 2019

ApJ

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We studied a flare onset process in terms of stability of a three-dimensional (3D) magnetic field in active region 12371 producing an eruptive M6.5 flare in 2015 June 22. In order to reveal the 3D magnetic structure, we first extrapolated the 3D coronal magnetic fields based on time series of the photospheric vector magnetic fields under a nonlinear force-free field (NLFFF) approximation. The NLFFFs nicely reproduced the observed sigmoidal structure which is widely considered as preeruptive magnetic configuration. We, in particular, found that the sigmoid is composed of two branches of sheared arcade loops. On the basis of the NLFFFs, we investigated the sheared arcade loops to explore the onset process of the eruptive flare using three representative MHD instabilities: the kink, torus and double arc instabilities. The double arc instability, recently proposed by Ishiguro & Kusano, is a double arc loop can be more easily destabilized than a torus loop. Consequently, the NLFFFs are found to be quite stable against the kink and torus instabilities. However, the sheared arcade loops formed prior to the flare possibly becomes unstable against the double arc instability. As a possible scenario on the onset process of the M6.5 flare, we suggest three-step process: (1) double arc loop are formed by the sheared arcade loops through the tether-cutting reconnection during an early phase of the flare, (2) the double arc instability contributes to the expansion of destabilized double arc loops and (3) finally, the torus instability makes the full eruption.

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Section: Observations and Numerical Methodsmentioning

confidence: 96%

Onset Mechanism of M6.5 Solar Flare Observed in Active Region 12371

Junsang¹,

Inoue²,

Kusano³

et al. 2019

ApJ

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“… 2009 ; Wang et al. 2009 , 2013 , 2018b ). The most prominent changes are the enhancement (i.e., darkening) of penumbral structure near the flaring PILs and the decay of penumbral structure in the peripheral sides (outer edges) of -spots.…”

Section: Rapid Changes Of Magnetic Fields Associated With Flaresmentioning

confidence: 99%

Flare-productive active regions

Toriumi

Wang

2019

Living Rev Sol Phys

Self Cite

246

151

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Strong solar flares and coronal mass ejections, here defined not only as the bursts of electromagnetic radiation but as the entire process in which magnetic energy is released through magnetic reconnection and plasma instability, emanate from active regions (ARs) in which high magnetic non-potentiality resides in a wide variety of forms. This review focuses on the formation and evolution of flare-productive ARs from both observational and theoretical points of view. Starting from a general introduction of the genesis of ARs and solar flares, we give an overview of the key observational features during the long-term evolution in the pre-flare state, the rapid changes in the magnetic field associated with the flare occurrence, and the physical mechanisms behind these phenomena. Our picture of flare-productive ARs is summarized as follows: subject to the turbulent convection, the rising magnetic flux in the interior deforms into a complex structure and gains high non-potentiality; as the flux appears on the surface, an AR with large free magnetic energy and helicity is built, which is represented by -sunspots, sheared polarity inversion lines, magnetic flux ropes, etc; the flare occurs when sufficient magnetic energy has accumulated, and the drastic coronal evolution affects magnetic fields even in the photosphere. We show that the improvement of observational instruments and modeling capabilities has significantly advanced our understanding in the last decades. Finally, we discuss the outstanding issues and future perspective and further broaden our scope to the possible applications of our knowledge to space-weather forecasting, extreme events in history, and corresponding stellar activities. Electronic supplementary material The online version of this article (10.1007/s41116-019-0019-7) contains supplementary material, which is available to authorized users.

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“…Panel (a) shows the vector change ∆B h between the two times (before and after the flare) shown in Figure 1. The field of view is a smaller than in Figure 1 Wang et al (2018) also showed (using high resolution images in the TiO band obtained with the Goode Solar Telescope combined with flow tracking), that the increase in the horizontal field was accompanied by oppositely directed shear flows on either side of the neutral line.…”

Section: June 2015 Flarementioning

confidence: 56%

Photospheric Response to a Flare

Wheatland

Melrose

Mastrano

2018

ApJ

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Flares produce sudden and permanent changes in the horizontal photospheric magnetic field. In particular flares generally produce increased magnetic shear in the photospheric field along the neutral line. Recent observations show also that flares can produce sudden photospheric motion. We present a model for the observed changes as the response of the photosphere to a large-amplitude shear Alfvén wave propagating down from the corona on either side of the neutral line. The Alfvénic front is assumed to impact the photosphere close to the neutral line first, and then successively further away with time, such that the line of impact coincides with the flare ribbon. The wave introduces magnetic shear and velocity shear. The magnetic shear introduced at the photosphere has the same sign on either side of the neutral line, while the velocity shear has the opposite sign. We discuss the possibility that this process is responsible for particle acceleration in flares.

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Evolution of Photospheric Flow and Magnetic Fields Associated with the 2015 June 22 M6.5 Flare

Cited by 20 publications

References 52 publications

Onset Mechanism of M6.5 Solar Flare Observed in Active Region 12371

Onset Mechanism of M6.5 Solar Flare Observed in Active Region 12371

Flare-productive active regions

Photospheric Response to a Flare

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