Two Types of Confined Solar Flares

Li, Ting; Liu, Lijuan; Hou, Yijun; Zhang, Jun

doi:10.3847/1538-4357/ab3121

Cited by 33 publications

(24 citation statements)

References 105 publications

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“…5. By analyzing the dynamic evolution of 26 confined flares occurring in ARs with Φ AR ≥1.0×10 23 Mx, we find that these flares have several characteristics in common: stable filament, slipping magnetic reconnection and strongly sheared PFLs, belonging to "type I" flares as proposed in our previous work (Li et al 2019).…”

Section: Summary and Discussionmentioning

confidence: 61%

“…The confined flares from ARs with Φ AR ≥1.0×10 23 Mx are characterized by slipping reconnection, strong shear, and a stable filament. They belong to "type I" confined flares proposed by Li et al (2019), who classified confined flares into two types based on their different dynamic properties and magnetic configurations. Similar to the appearance of confined flares in AR 12192 (Li et al 2019), the filaments in ARs 11339, 11520 (Figures 6-7), 11967 and 12242 (Figures 8-9) were all stably present and seemed not to be involved in the flare evolution.…”

Section: Summary and Discussionmentioning

confidence: 99%

“…They belong to "type I" confined flares proposed by Li et al (2019), who classified confined flares into two types based on their different dynamic properties and magnetic configurations. Similar to the appearance of confined flares in AR 12192 (Li et al 2019), the filaments in ARs 11339, 11520 (Figures 6-7), 11967 and 12242 (Figures 8-9) were all stably present and seemed not to be involved in the flare evolution. The footpoints of high-temperature flare loops exhibited apparent slipping motions in both directions along flare ribbons (Figure 9), which implies the occurrence of slipping magnetic reconnection overlying the non-eruptive filaments (Li & Zhang 2015;Dudík et al 2016;Lörinčík et al 2019;Shen et al 2019;Chen et al 2019).…”

Section: Summary and Discussionmentioning

confidence: 99%

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Magnetic Flux of Active Regions Determining the Eruptive Character of Large Solar Flares

Li¹,

Hou²,

Yang³

et al. 2020

Preprint

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We establish the largest eruptive/confined flare database to date and analyze 322 flares of GOES class M1.0 and larger that occurred during 2010−2019, i.e., almost spanning the entire solar cycle 24. We find that the total unsigned magnetic flux (Φ AR ) of active regions (ARs) is a key parameter in governing the eruptive character of large flares, with the proportion of eruptive flares exhibiting a strong anti-correlation with Φ AR . This means that an AR containing a large magnetic flux has a lower probability for the large flares it produces to be associated with a coronal mass ejection (CME). This finding is supported by the high positive correlation we obtained between the critical decay index height and Φ AR , implying that ARs with a larger Φ AR have a stronger magnetic confinement. Moreover, the confined flares originating from ARs larger than 1.0×10 23 Mx have several characteristics in common: stable filament, slipping magnetic reconnection and strongly sheared post-flare loops. Our findings reveal new relations between the magnetic flux of ARs and the occurrence of CMEs in association with large flares. These relations obtained here provide quantitative criteria for forecasting CMEs and adverse space weather, and have also important implications for "superflares" on solar-type stars and stellar CMEs. The link of database

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Section: Summary and Discussionmentioning

confidence: 61%

Section: Summary and Discussionmentioning

confidence: 99%

Section: Summary and Discussionmentioning

confidence: 99%

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Magnetic Flux of Active Regions Determining the Eruptive Character of Large Solar Flares

Li¹,

Hou²,

Yang³

et al. 2020

Preprint

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“…If a flux rope in an active region remains stable (or is even entirely absent), reconnection between sheared magnetic fields can still lead to flares without a CME (Li et al 2019), a scenario that has been proposed to explain the observed behaviour of NOAA active region 12192 (Jiang et al 2016). This scenario may serve as another resolution to the missing stellar CME conundrum, but it remains to be seen how frequently such flares actually occur.…”

Section: Summary and Discussionmentioning

confidence: 99%

Torus-Stable Zone Above Starspots

Sun,

Török,

DeRosa

2021

Preprint

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Whilst intense solar flares are almost always accompanied by a coronal mass ejection (CME), reports on stellar CMEs are rare, despite the frequent detection of stellar 'super flares'. The torus instability of magnetic flux ropes is believed to be one of the main driving mechanisms of solar CMEs. Suppression of the torus instability, due to a confining background coronal magnetic field that decreases sufficiently slowly with height, may contribute to the lack of stellar CME detection. Here we use the solar magnetic field as a template to estimate the vertical extent of this 'torus-stable zone' (TSZ) above a stellar active region. For an idealised potential field model comprising the fields of a local bipole (mimicking a pair of starspots) and a global dipole, we show that the upper bound of the TSZ increases with the bipole size, the dipole strength, and the source surface radius where the coronal field becomes radial. The boundaries of the TSZ depend on the interplay between the spots' and the dipole's magnetic fields, which provide the local-and global-scale confinement, respectively. They range from about half the bipole size to a significant fraction of the stellar radius. For smaller spots and an intermediate dipole field, a secondary TSZ arises at a higher altitude, which may increase the likelihood of 'failed eruptions'. Our results suggest that the low apparent CME occurrence rate on cool stars is, at least partially, due to the presence of extended TSZs.

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“…The characteristics of eruptive flares have been well described by the standard flare model. The characteristics of confined flares are studied by comparison of the physical parameters between the eruptive and confined flares (Falconer et al 2006;Kliem & Török 2006;Cheng et al 2011;Harra et al 2016;Zhang et al 2017;Li et al 2019). Those studies suggest that the magnetic configuration, such as overlying field strength, decay index, and non-potentiality of an active region core, could be a determining factor of a confined flare.…”

Section: Introductionmentioning

confidence: 99%

A Solar Magnetic-fan Flaring Arch Heated by Non-thermal Particles and Hot Plasma from an X-ray Jet Eruption

Lee,

Hara,

Watanabe

et al. 2020

Preprint

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We have investigated an M1.3 limb flare, which develops as a magnetic loop/arch that fans out from an X-ray jet. Using Hinode/EIS, we found that the temperature increases with height to a value of over 10 7 K at the loop-top during the flare. The measured Doppler velocity (redshifts of 100−500 km s −1 ) and the non-thermal velocity (≥100 km s −1 ) from Fe XXIV also increase with loop height. The electron density increases from 0.3 × 10 9 cm −3 early in the flare rise to 1.3 × 10 9 cm −3 after the flare peak. The 3-D structure of the loop derived with STEREO/EUVI indicates that the strong redshift in the loop-top region is due to upflowing plasma originating from the jet. Both hard X-ray and soft X-ray emission from RHESSI were only seen as footpoint brightenings during the impulsive phase of the flare, then, soft X-ray emission moves to the loop-top in the decay phase. Based on the temperature and density measurements and theoretical cooling models, the temperature evolution of the flare arch is consistent with impulsive heating during the jet eruption followed by conductive cooling via evaporation and minor prolonged heating in the top of the fan loop. Investigating the magnetic field topology and squashing factor map from SDO/HMI, we conclude that the observed magnetic-fan flaring arch is mostly heated from low atmospheric reconnection accompanying the jet ejection, instead of from reconnection above the arch as expected in the standard flare model.

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Two Types of Confined Solar Flares

Cited by 33 publications

References 105 publications

Magnetic Flux of Active Regions Determining the Eruptive Character of Large Solar Flares

Magnetic Flux of Active Regions Determining the Eruptive Character of Large Solar Flares

Torus-Stable Zone Above Starspots

A Solar Magnetic-fan Flaring Arch Heated by Non-thermal Particles and Hot Plasma from an X-ray Jet Eruption

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