Are Complex Magnetic Field Structures Responsible for the Confined X-class Flares in Super Active Region 12192?

Zhang, Jun; Li, Ting; Chen, Huadong

doi:10.3847/1538-4357/aa7e7d

Cited by 12 publications

(13 citation statements)

References 49 publications

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“…The average orientation of the PIL is determined from the HMI LOS magnetogram prior to the flare onset. The inclination angle θ corresponds to the angle between the tangents of the PFL and PIL at their intersection (panel (b)), which is consistent with the method of Zhang et al (2017). The complementary angle of θ has been referred to as the shear angle in previous studies (Su et al 2007;Aulanier et al 2012).…”

Section: Resultssupporting

confidence: 69%

Two Types of Confined Solar Flares

Liu

Hou

et al. 2019

ApJ

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With the aim of understanding the physical mechanisms of confined flares, we selected 18 confined flares during 2011-2017, and classified the confined flares into two types based on their different dynamic properties and magnetic configurations. "Type I" of confined flares are characterized by slipping reconnection, strong shear, and stable filament. "Type II" flares have nearly no slipping reconnection, and have a configuration in potential state after the flare. Filament erupts but is confined by strong strapping field. "Type II" flares could be explained by 2D MHD models while "type I" flares need 3D MHD models. 7 flares of 18 (∼39 %) belong to "type I" and 11 (∼61 %) are "type II" confined flares. The post-flare loops (PFLs) of "type I" flares have a stronger non-potentiality, however, the PFLs in "type II" flares are weakly sheared. All the "type I" flares exhibit the ribbon elongations parallel to the polarity inversion line (PIL) at speeds of several tens of km s −1 . For "type II" flares, only a small proportion shows the ribbon elongations along the PIL. We suggest that different magnetic topologies and reconnection scenarios dictate the distinct properties for the two types of flares. Slipping magnetic reconnections between multiple magnetic systems result in "type I" flares. For "type II" flares, magnetic reconnections occur in anti-parallel magnetic fields underlying the erupting filament. Our study shows that "type I" flares account for more than one third of the overall large confined flares, which should not be neglected in further studies.

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Section: Resultssupporting

confidence: 69%

Two Types of Confined Solar Flares

Liu

Hou

et al. 2019

ApJ

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“…This result is similar to the earlier finding by Cheng et al (2011) where they did a comparative study of the critical decay index (1.5) height for the onset of the torus instability over both the eruptive and non-eruptive regions belonging to same AR (NOAA AR 10720). Although our study suggests the importance of the background magnetic field strength for the confined behavior of the non-eruptive flares, a recent study (Zhang, Li, and Chen, 2017) reveals that the complex flare loops associated with the non-eruptive flares originating from AR 12192 may also be responsible for the confinement.…”

Section: Discussionmentioning

confidence: 78%

A Comparative Study of the Eruptive and Non-eruptive Flares Produced by the Largest Active Region of Solar Cycle 24

Sarkar

Srivastava

2018

Sol Phys

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We investigate the morphological and magnetic characteristics of solar active region (AR) NOAA 12192. AR 12192 was the largest region of Solar Cycle 24; it underwent noticeable growth and produced 6 X-class flares, 22 M-class flares, and 53 C-class flares in the course of its disc passage. However, the most peculiar fact of this AR is that it was associated with only one CME in spite of producing several X-class flares. In this work, we carry out a comparative study between the eruptive and non-eruptive flares produced by AR 12192. We find that the magnitude of abrupt and permanent changes in the horizontal magnetic field and Lorentz force are significantly smaller in the case of the confined flares compared to the eruptive one. We present the areal evolution of AR 12192 during its disc passage. We find the flare-related morphological changes to be weaker during the confined flares, whereas the eruptive flare exhibits a rapid and permanent disappearance of penumbral area away from the magnetic neutral line after the flare. Furthermore, from the extrapolated nonlinear force-free magnetic field, we examine the overlying coronal magnetic environment over the eruptive and non-eruptive zones of the AR. We find that the critical decay index for the onset of torus instability was achieved at a lower height over the eruptive flaring region, than for the non-eruptive core area. These results suggest that the decay rate of the gradient of overlying magnetic field strength may play a decisive role to determine the CME productivity of the AR. In addition, the magnitude of changes in the flare-related magnetic characteristics are found to be well correlated with the nature of solar eruptions.

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“…Similar results were also documented in Chen et al (2015), where the mean decay index of the horizontal background field was found to be less than the typical threshold required for the torus instability (Kliem & Török 2006) to set in. An alternative explanation was provided by Zhang et al (2017) who attributed the confined nature to the complexity of the involved magnetic field structures.…”

Section: Discussion On the X31 Flare Eventmentioning

confidence: 99%

A Magnetohydrodynamic Simulation of Magnetic Null-point Reconnections in NOAA AR 12192, Initiated with an Extrapolated Non-force-free Field

Prasad

Bhattacharyya

et al. 2018

ApJ

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Magnetohydrodynamics of the solar corona is simulated numerically. The simulation is initialized with an extrapolated non-force-free magnetic field using the vector magnetogram of the active region (AR) NOAA 12192 obtained on the solar photosphere. Particularly, we focus on the magnetic reconnections occurring close to a magnetic null-point that resulted in appearance of circular chromospheric flare ribbons on October 24, 2014 around 21:21 UT, after peak of an X3.1 flare. The extrapolated field lines show the presence of the threedimensional (3D) null near one of the polarity inversion lines-where the flare was observed. In the subsequent numerical simulation, we find magnetic reconnections occurring near the null point, where the magnetic field lines from the fan-plane of the 3D null form a X-type configuration with underlying arcade field lines. The footpoints of the dome-shaped field lines, inherent to the 3D null, show high gradients of the squashing factor. We find slipping reconnections at these quasi-separatrix layers, which are co-located with the post-flare circular brightening observed at the chromospheric heights. This demonstrates the viability of arXiv:1805.00635v1 [astro-ph.SR] 2 May 2018 the initial non-force-free field along with the dynamics it initiates. Moreover, the initial field and its simulated evolution is found to be devoid of any flux rope, which is in congruence with the confined nature of the flare.

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Are Complex Magnetic Field Structures Responsible for the Confined X-class Flares in Super Active Region 12192?

Cited by 12 publications

References 49 publications

Two Types of Confined Solar Flares

Two Types of Confined Solar Flares

A Comparative Study of the Eruptive and Non-eruptive Flares Produced by the Largest Active Region of Solar Cycle 24

A Magnetohydrodynamic Simulation of Magnetic Null-point Reconnections in NOAA AR 12192, Initiated with an Extrapolated Non-force-free Field

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