Formation of a Flare-Productive Active Region: Observation and Numerical Simulation of NOAA AR 11158

Toriumi, Shin; Iida, Yusuke; Kusano, K.; Bamba, Yumi; Imada, Shinsuke

doi:10.1007/s11207-014-0502-1

Cited by 55 publications

(65 citation statements)

References 37 publications

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“…Early observational studies [2,3] propose that δ-sunspots form from collision-merging of topologically separate dipoles, while numerical simulations by [4,5] show that kink unstable magnetic flux-tube -helical field lines winding around a central axis -emerging from the subsurface can have a δ-sunspot like structure. More recently, attempts to model the δ-spot in the NOAA AR 11158 utilized a uniformly twisted sub-surface flux-tube initially buoyant in two adjacent regions along its length [6,7]. Also, [8] found a magnetic flux concentration resembling a δ sunspot in their stratified helical dynamo simulation.…”

mentioning

confidence: 99%

Modeling Repeatedly FlaringδSunspots

Chatterjee¹,

Hansteen²,

Carlsson³

2016

Phys. Rev. Lett.

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Active regions (AR) appearing on the surface of the Sun are classified into α, β, γ, and δ by the rules of the Mount Wilson Observatory, California on the basis of their topological complexity. Amongst these, the δ-sunspots are known to be super-active and produce the most X-ray flares. Here, we present results from a simulation of the Sun by mimicking the upper layers and the corona, but starting at a more primitive stage than any earlier treatment. We find that this initial state consisting of only a thin sub-photospheric magnetic sheet breaks into multiple flux-tubes which evolve into a colliding-merging system of spots of opposite polarity upon surface emergence, similar to those often seen on the Sun. The simulation goes on to produce many exotic δ-sunspot associated phenomena: repeated flaring in the range of typical solar flare energy release and ejective helical flux ropes with embedded cool-dense plasma filaments resembling solar coronal mass ejections.Delta-sunspots are formed when two sunspots of opposite polarity magnetic field appear very close to each other and reside in the same penumbra, the radial filamentary structure outside the umbral region of the strongest magnetic fields. Strong shear and horizontal magnetic fields often exist at the polarity-inversion line separating the two polarities [1]. The subsurface processes which form the δ-sunspots are still debated. Early observational studies [2,3] propose that δ-sunspots form from collision-merging of topologically separate dipoles, while numerical simulations by [4,5] show that kink unstable magnetic flux-tube -helical field lines winding around a central axis -emerging from the subsurface can have a δ-sunspot like structure. More recently, attempts to model the δ-spot in the NOAA AR 11158 utilized a uniformly twisted sub-surface flux-tube initially buoyant in two adjacent regions along its length [6,7]. Also, [8] found a magnetic flux concentration resembling a δ sunspot in their stratified helical dynamo simulation. These studies did not report any flaring activity. On the other hand [9] initialized their simulation with two parallel flux-tubes each lying at a different depth from the surface and with a different value of the initial magnetic twist which later evolved into a δ-sunspot like structure and powered multiple reconnection events. Delta-sunspots are highly flare-productive -95% of the strongest (X-class) X-ray flares originate from these regions [3]. Using a realistic numerical simulation [10] showed that interaction between adjacent expanding magnetic bipoles pressing against each other can lead to the formation of strong current layers in the atmosphere which in turn lead to repeated flaring in the region. Here, we report on a three-dimensional magneto-hydrodynamic (MHD) simulation of the formation of a δ-sunpot like region as a result of the break-up of a cool magnetic layer embedded in the upper solar convection zone into several flux-tubes due to the growth of three-dimensional unstable modes excited in the layer. This instab...

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confidence: 99%

Modeling Repeatedly FlaringδSunspots

Chatterjee¹,

Hansteen²,

Carlsson³

2016

Phys. Rev. Lett.

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“…This event consequently received much attention in the literature, starting with . Toriumi et al (2014) (see also Janvier et al 2014) describe the evolution of the surface field of the region and of its coronal configuration up to the point of the X2.2 flare. They apply MHD modeling of the flux emergence to gain insight into the formation of the highly sheared strong-field polarity inversion line involved in the onset of the flare and coronal mass ejection.…”

Section: Ar 11158mentioning

confidence: 99%

The Nonpotentiality of Coronae of Solar Active Regions, the Dynamics of the Surface Magnetic Field, and the Potential for Large Flares

Schrijver

2016

ApJ

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Flares and eruptions from solar active regions (ARs) are associated with atmospheric electrical currents accompanying distortions of the coronal field away from a lowest-energy potential state. In order to better understand the origin of these currents and their role in M-and X-class flares, I review all AR observations made with Solar Dynamics Observatory (SDO)/Helioseismic and Magnetic Imager and SDO/Atmospheric Imaging Assembly from 2010 May through 2014 October within ≈40°from the disk center. I select the roughly 4% of all regions that display a distinctly nonpotential coronal configuration in loops with a length comparable to the scale of the AR, and all that emit GOES X-class flares. The data for 41 regions confirm, with a single exception, that strong-field, high-gradient polarity inversion lines (SHILs) created during emergence of magnetic flux into, and related displacement within, pre-existing ARs are associated with X-class flares. Obvious nonpotentiality in the AR-scale loops occurs in six of ten selected regions with X-class flares, all with relatively long SHILs along their primary polarity inversion line, or with a long internal filament there. Nonpotentiality can exist in ARs well past the flux-emergence phase, often with reduced or absent flaring. I conclude that the dynamics of the flux involved in the compact SHILs is of pre-eminent importance for the large-flare potential of ARs within the next day, but that their associated currents may not reveal themselves in AR-scale nonpotentiality. In contrast, AR-scale nonpotentiality, which can persist for many days, may inform us about the eruption potential other than those from SHILs which is almost never associated with X-class flaring.

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“…As a example, Toriumi et al (2014) carried out numerical magnetohydrodynamics simulations of the rise of buoyant flux tubes to mimic the observed photospheric evolution of sunspots in NOAA AR 11158. This active region appeared on the photosphere as two pairs of magnetic bipoles, and evolved such that the following polarity of one bipole jousted against the leading polarity of the other bipole, resulting in a sheared polarity inversion line which subsequently produced an X-class flare and CME.…”

Section: The Subsurface Origin Of Active Region Magnetic Fieldsmentioning

confidence: 99%

“…This active region appeared on the photosphere as two pairs of magnetic bipoles, and evolved such that the following polarity of one bipole jousted against the leading polarity of the other bipole, resulting in a sheared polarity inversion line which subsequently produced an X-class flare and CME. Toriumi et al (2014) carried out simulations with initial conditions that consist of (i) two adjacent, submerged flux tubes each with a buoyant segment, and (ii) a single submerged tube with two magnetically buoyant segments. Both initial conditions yielded a pair of bipoles emerging at the surface, but only the latter case resulted in a sheared polarity inversion line amenable for eruptive activity.…”

Section: The Subsurface Origin Of Active Region Magnetic Fieldsmentioning

confidence: 99%