Statistical investigation on the formation of sunspot light bridges

Li, Fuyu; Chen, Yuhao; Song, Yongliang; Hou, Zhenyong

doi:10.1088/1674-4527/21/6/144

Cited by 6 publications

(22 citation statements)

References 51 publications

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“…There are small-scale activities above LBs, such as Hα surges, light-wall oscillations, and small-scale bright blobs ejected from the sunspot LB, which could heat the chromosphere and transition region in a sustained manner (Tian et al 2018;Bai et al 2019;Zheng et al 2019;Li et al 2021a;Hou et al 2022;Louis et al 2023). Li et al (2021b) classified LBs based on their formation processes, and presented the first statistical investigation into the formation of LBs. They divided these formation processes into three categories: penumbral intrusion (type-A), sunspot merging (type-B), and umbral-dot emergence (type-C); (Li et al 2021b).…”

Section: Introductionmentioning

confidence: 99%

“…Li et al (2021b) classified LBs based on their formation processes, and presented the first statistical investigation into the formation of LBs. They divided these formation processes into three categories: penumbral intrusion (type-A), sunspot merging (type-B), and umbral-dot emergence (type-C); (Li et al 2021b). Type-A LBs are formed when some parts of the penumbrae intrude toward the umbrae (Rimmele 2004;Katsukawa et al 2007;Ortiz et al 2010;Hou et al 2020), which is the most common process (Li et al 2021b).…”

Section: Introductionmentioning

confidence: 99%

“…They divided these formation processes into three categories: penumbral intrusion (type-A), sunspot merging (type-B), and umbral-dot emergence (type-C); (Li et al 2021b). Type-A LBs are formed when some parts of the penumbrae intrude toward the umbrae (Rimmele 2004;Katsukawa et al 2007;Ortiz et al 2010;Hou et al 2020), which is the most common process (Li et al 2021b). A positive correlation between the duration of the formation process and the length of the LB suggests a similar speed of penumbral intrusion in different sunspots (Li et al 2021b).…”

Section: Introductionmentioning

confidence: 99%

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Light Bridges and Solar Active Region Evolution Processes

Li,

Rao,

Zhao

et al. 2024

ApJS

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The formation mechanism of light bridges (LBs) is strongly related to the dynamic evolution of solar active regions (ARs). To study the relationship between LB formation and AR evolution phases, we employ 109 LB samples from 69 ARs in 2014 using observational data from the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory. LBs are well matched with the weak field lanes (WFLs), except those aligned on the polarity inversion line of δ sunspots. For penumbral intrusion (type-A) and umbral-dot emergence (type-C) LBs, the WFLs represent the splitting of magnetic flux systems. The sunspots tend to decay and split into several parts after type-A and type-C LBs are formed. For sunspot/umbra-merging (type-B) LBs, the declining WFLs are caused by collisions of flux systems. The sunspots merged and remained stable after type-B LBs formed. We conclude that type-B LBs are formed by collisions of flux systems, while type-A and type-C LBs are generated by splits. The time differences (δ T) between LBs appearing and ARs peaking have an average value of 1.06, −1.60, and 1.82 days for type-A, B, and C LBs, with the standard deviations of 3.27, 2.17, and 1.89, respectively. A positive value of δ T means that the LB appears after the AR peaks, whereas a negative δ T means it appears before the peak. Type-A LBs tend to form in the decaying phase or around the peak time. Type-B LBs are more likely to be formed in the developing phase. Type-C LBs mostly take shape in the decaying phase of ARs.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Light Bridges and Solar Active Region Evolution Processes

Li,

Rao,

Zhao

et al. 2024

ApJS

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“…Regarding the LB formation, Schlichenmaier et al (2010) and Rezaei et al (2012) witnessed the formation of a thick LB within a sunspot caused by coalescence of two pores with the same magnetic polarity (Garcia de La Rosa 1987; Berger & Berdyugina 2003). LBs can also form through the rapid intrusion of sunspot penumbral filaments into the umbra, accompanied by many umbral dots emerging from the leading edges of the filaments (Katsukawa et al 2007;Li et al 2021b). It is worth noting that within the special delta-type sunspot, the collision of two rotating umbrae of opposite polarities can produce a delta-spot LB with very strong and sheared horizontal magnetic fields (Zirin & Wang 1993;Livingston et al 2006;Okamoto & Sakurai 2018;Toriumi & Hotta 2019;Castellanos Durán et al 2020).…”

Section: Introductionmentioning

confidence: 99%

Various Activities above Sunspot Light Bridges in IRIS Observations: Classification and Comparison

Hou,

Li,

Yang

et al. 2022

Preprint

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Light bridges (LBs) are among the most striking sub-structures in sunspots, where various activities have been revealed by recent high-resolution observations from the Interface Region Imaging Spectrograph (IRIS ). According to the variety of physical properties, we classified these activities into four distinct categories: transient brightening (TB), intermittent jet (IJ), type-I light wall (LW-I), and type-II light wall (LW-II). In IRIS 1400/1330 Å observations, TBs are characterized by abrupt emission enhancements, and IJs appear as collimated plasma ejections with a width of 1-2 Mm at some LB sites. Most observed TBs are associated with IJs and show superpositions of some chromosphere absorption lines on enhanced and broadened wings of C ii and Si iv lines, which could be driven by intermittent magnetic reconnection in the lower atmosphere. LW-I and LW-II are wall-shaped structures with bright fronts above the whole LB. An LW-I has a continuous oscillating front with a typical height of several Mm and an almost stationary period of 4-5 minutes. On the contrary, an LW-II has a indented front with a height of over 10 Mm, which has no stable period and is accompanied by recurrent TBs in the entire LB. These results support that LW-IIs are driven by frequent reconnection occurring along the whole LB due to large-scale magnetic flux emergence or intrusion, rather than the leakage of waves producing LW-Is. Our observations reveal a highly dynamical scenario of activities above LBs driven by different basic physical processes, including magneto-convection, magnetic reconnection, and wave leakage.

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“…Some reports say that their lifetime tends to be short, sometimes no longer than one day (e.g., Vazquez 1973), while other light bridges can be followed for many days (e.g., Katsukawa et al 2007). To our knowledge, there is just one recent report by Li et al (2021) that has analyzed the mean lifetime of light bridges statistically. Based on a simplified analysis, the authors found that the average time of formation of light bridges is ∼20 hr, and no longer than 40 hr.…”

Section: Light Bridgesmentioning

confidence: 99%

Strong magnetic fields and unusual flows in sunspots

Duran¹

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Statistical investigation on the formation of sunspot light bridges

Cited by 6 publications

References 51 publications

Light Bridges and Solar Active Region Evolution Processes

Light Bridges and Solar Active Region Evolution Processes

Various Activities above Sunspot Light Bridges in IRIS Observations: Classification and Comparison

Strong magnetic fields and unusual flows in sunspots

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