NUMERICAL STUDY ON THE EMERGENCE OF KINKED FLUX TUBE FOR UNDERSTANDING OF POSSIBLE ORIGIN OF<i>δ</i>-SPOT REGIONS

Takasao, Shinsuke; Fan, Yuhong; Cheung, Mark C. M.; Shibata, Kazunari

doi:10.1088/0004-637x/813/2/112

Cited by 52 publications

(68 citation statements)

References 47 publications

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“…However, Billinghurst et al (1993) explained that strong currents could develop at least near the footpoints of the BP separatrix because a strong concentration of flux tubes could be present in these regions. More recently, Pariat et al (2009b) showed that currents can accumulate at BPs and their separatrices in MHD numercial simulations; while other simulations like those by Archontis & Hood (2009), Archontis et al (2013), Cheung et al (2010), and Takasao et al (2015) have shown the development of magnetic reconnection at BPs during the build up of ARs.…”

Section: The Local Magnetic-field Modelmentioning

confidence: 96%

Blowout jets and impulsive eruptive flares in a bald-patch topology

Chandra

Mandrini

Schmieder

et al. 2017

A&A

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Context. A subclass of broad EUV and X-ray jets, called blowout jets, have become a topic of research since they could be the link between standard collimated jets and CMEs. Aims. Our aim is to understand the origin of a series of broad jets, some accompanied by flares and associated with narrow and jet-like CMEs. Methods. We analyze observations of a series of recurrent broad jets observed in AR 10484 on 21 -24 October 2003. In particular, one of them occurred simultaneously with an M2.4 flare on 23 October at 02:41 UT (SOLA2003-10-23). Both events were observed by ARIES Hα Solar Tower-Telescope, TRACE, SOHO, and RHESSI instruments. The flare was very impulsive and followed by a narrow CME. A local force-free model of AR 10484 is the basis to compute its topology. We find bald patches (BPs) at the flare site. This BP topology is present for at least two days before. Large-scale field lines, associated with the BPs, represent open loops. This is confirmed by a global PFSS model. Following the brightest leading edge of the Hα and EUV jet emission, we can temporarily associate it with a narrow CME. Results. Considering their characteristics, the observed broad jets appear to be of the blowout class. As the most plausible scenario, we propose that magnetic reconnection could occur at the BP separatrices forced by the destabilization of a continuously reformed flux rope underlying them. The reconnection process could bring the cool flux-rope material into the reconnected open field lines driving the series of recurrent blowout jets and accompanying CMEs. Conclusions. Based on a model of the coronal field, we compute the AR 10484 topology at the location where flaring and blowout jets occurred from 21 to 24 October 2003. This topology can consistently explain the origin of these events.

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Section: The Local Magnetic-field Modelmentioning

confidence: 96%

Blowout jets and impulsive eruptive flares in a bald-patch topology

Chandra

Mandrini

Schmieder

et al. 2017

A&A

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“…Among the 11 ARs (21 events) that belong to this category (see bottom of Figure 6), NOAA AR 11429 produced the strongest (X5.4-class) flare so far in this solar cycle. Based on the numerical simulation of flux emergence, Takasao et al (2015) suggested the possibility that AR 11429 was created by an emergence of a tightly-twisted, kink-unstable flux tube (see also, e.g., Tanaka 1991;Linton et al 1996;Fan et al 1998). The spot-spot may also be created by many episodes of flux emergence.…”

Section: Magnetic Patterns Of Flare Zonesmentioning

confidence: 99%

“…Therefore, we need a systematic survey using flux emergence simulations to model these types of ARs (Toriumi et al 2014a;Fang & Fan 2015;Takasao et al 2015;Chatterjee et al 2016) and investigate their formation processes as well as the storage of magnetic energy (amount, place, etc.). In Figure 4, we found that S ribbon /S spot and |Φ| ribbon /|Φ| AR are larger for the CME-eruptive events, which may indicate the importance of the relative magnetic structure of the flaring region and the entire AR.…”

Section: Emergence Flares and Superflaresmentioning

confidence: 99%

Magnetic Properties of Solar Active Regions That Govern Large Solar Flares and Eruptions

Toriumi

Schrijver

Harra³

et al. 2017

ApJ

160

123

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Solar flares and coronal mass ejections (CMEs), especially the larger ones, emanate from active regions (ARs). With the aim to understand the magnetic properties that govern such flares and eruptions, we systematically survey all flare events with GOES levels of ≥ M5.0 within 45• from disk center between May 2010 and April 2016. These criteria lead to a total of 51 flares from 29 ARs, for which we analyze the observational data obtained by the Solar Dynamics Observatory. More than 80% of the 29 ARs are found to exhibit δ-sunspots and at least three ARs violate Hale's polarity rule. The flare durations are approximately proportional to the distance between the two flare ribbons, to the total magnetic flux inside the ribbons, and to the ribbon area. From our study, one of the parameters that clearly determine whether a given flare event is CME-eruptive or not is the ribbon area normalized by the sunspot area, which may indicate that the structural relationship between the flaring region and the entire AR controls CME productivity. AR characterization show that even X-class events do not require δ-sunspots or strong-field, high-gradient polarity inversion lines. An investigation of historical observational data suggests the possibility that the largest solar ARs, with magnetic flux of 2×10 23 Mx, might be able to produce "superflares" with energies of order of 10 34 erg. The proportionality between the flare durations and magnetic energies is consistent with stellar flare observations, suggesting a common physical background for solar and stellar flares.

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“…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].…”

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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NUMERICAL STUDY ON THE EMERGENCE OF KINKED FLUX TUBE FOR UNDERSTANDING OF POSSIBLE ORIGIN OFδ-SPOT REGIONS

Cited by 52 publications

References 47 publications

Blowout jets and impulsive eruptive flares in a bald-patch topology

Blowout jets and impulsive eruptive flares in a bald-patch topology

Magnetic Properties of Solar Active Regions That Govern Large Solar Flares and Eruptions

Modeling Repeatedly FlaringδSunspots

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