Flame-like Ellerman Bombs and Their Connection to Solar Ultraviolet Bursts

Chen, Yajie; Peter, Hardi; Samanta, Tanmoy; Yurchyshyn, Vasyl; Wang, Haimin; Cao, Wenda; Wang, Linghua; He, Jiansen

doi:10.3847/2041-8213/ab18a4

Cited by 42 publications

(45 citation statements)

References 49 publications

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“…So, our results demonstrate that, in cancelling regions, a wide spectrum of ejections can be produced, with a wide range of different temperatures and sizes associated with Ellerman bombs, UV bursts and IRIS bombs and other hot and cool ejections (Yang et al 2013;Vissers et al 2015;Reid et al 2016;Rutten 2016;Nelson et al 2017;Rouppe van der Voort et al 2017;Young et al 2018;Tian et al 2018;Chen et al 2019;Guglielmino et al 2019;Ortiz et al 2020;Tiwari et al 2019;Huang et al 2019;Madjarska 2019). The predicted spatial offsets and time delays for hot and cool ejections are in accordance with observational findings.…”

Section: Discussionsupporting

confidence: 88%

A Cancellation Nanoflare Model for Solar Chromospheric and Coronal Heating. III. 3D Simulations and Atmospheric Response

Syntelis

Priest

2020

ApJ

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Inspired by recent observations suggesting that photospheric magnetic flux cancellation occurs much more frequently than previously thought, we analytically estimated the energy released from reconnection driven by photospheric flux cancellation, and proposed that it can act as a mechanism for chromospheric and coronal heating (Priest et al. 2018). Using two-dimensional simulations we validated the analytical estimates and studied the resulting atmospheric response (Syntelis et al. 2019). In the present work, we set up three-dimensional resistive MHD simulations of two cancelling polarities in a stratified atmosphere with a horizontal external field to further validate and improve upon the analytical estimates. The computational evaluation of the parameters associated with the energy release are in good qualitative agreement with the analytical estimates. The computational Poynting energy flux into the current sheet is in good qualitative agreement with the analytical estimates, after correcting the analytical expression to better account for the horizontal extent of the current sheet. The atmospheric response to the cancellation is the formation of hot ejections, cool ejections, or a combination of both hot and cool ejections, which can appear with a time difference and/or be spatially offset, depending on the properties of the cancelling region and the resulting height of the reconnection. Therefore, during the cancellation, a wide spectrum of ejections can be formed, which can account for the variety of multi-thermal ejections associated with Ellerman bombs, UV bursts and IRIS bombs, and also other ejections associated with small-scale cancelling regions and spicules.

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Section: Discussionsupporting

confidence: 88%

A Cancellation Nanoflare Model for Solar Chromospheric and Coronal Heating. III. 3D Simulations and Atmospheric Response

Syntelis

Priest

2020

ApJ

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“…This is because the (horizontal) motions in the high-β regions that push together oppositely directed magnetic field are not present. On the other hand, in a scenario in which an Ellerman bomb is initiated, one might well expect this to also induce effects at higher temperatures resembling UV bursts; this has indeed been suggested recently based on observations by Chen et al (2019). Therefore, one might speculate that a higher fraction of Ellerman bombs is accompanied by UV bursts, rather than the other way round.…”

Section: Relation To Ellerman Bombs and High-β Reconnectionmentioning

confidence: 67%

Plasmoid-mediated reconnection in solar UV bursts

Peter

Huang²,

Chitta

et al. 2019

A&A

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Context. Ultraviolet bursts are transients in the solar atmosphere with an increased impulsive emission in the extreme UV lasting for one to several tens of minutes. They often show spectral profiles indicative of a bi-directional outflow in response to magnetic reconnection. Aims. To understand UV bursts, we study how motions of magnetic elements at the surface can drive the self-consistent formation of a current sheet resulting in plasmoid-mediated reconnection. In particular, we want to study the role of the height of the reconnection in the atmosphere. Methods. We conducted numerical experiments solving the 2D magnetohydrodynamic equations from the solar surface to the upper atmosphere. Motivated by observations, we drove a small magnetic patch embedded in a larger system of magnetic field of opposite polarity. This type of configuration creates an X-type neutral point in the initial potential field. The models are characterized by the (average) plasma-β at the height of this X point. Results. The driving at the surface stretches the X-point into a thin current sheet, where plasmoids appear, accelerating the reconnection, and a bi-directional jet forms. This is consistent with what is expected for UV bursts or explosive events, and we provide a self-consistent model of the formation of the reconnection region in such events. The gravitational stratification gives a natural explanation for why explosive events are restricted to a temperature range around a few 0.1 MK, and the presence of plasmoids in the reconnection process provides an understanding of the observed variability during the transient events on a timescale of minutes. Conclusions. Our numerical experiments provide a comprehensive understanding of UV bursts and explosive events, in particular of how the atmospheric response changes if the reconnection happens at different plasma-β, that is, at different heights in the atmosphere. This analysis also gives new insight into how UV bursts might be related to the photospheric Ellerman bombs.

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“…A U-shaped magnetic field structure, the bottom of which touches the photosphere, was seen in the flare region (Fig.5a, b). Such magnetic field structures often result from interaction between emerging magnetic fields and convection flows (Pariat et al 2004;Xu et al 2010;Danilovic 2017), and magnetic reconnection between the oppositely directed magnetic field lines at the two sides of a U-shaped structure could lead to the generation of UV bursts and other similar events (Georgoulis et al 2004;Peter et al 2014;Chen et al 2019a, Chen et al 2019b). In our case, the two sides of the U-shaped structure are the opposite-polarity magnetic fields of the two small sunspots.…”

Section: Resultsmentioning

confidence: 99%

“…It is worth mentioning that one side of a U-shaped structure may reconnect with the surrounding magnetic field during flux emergence (e.g., Syntelis et al 2019;Chen et al 2019a). In principle this process could produce a flare.…”

Section: Resultsmentioning

confidence: 99%

A White-light Flare Powered by Magnetic Reconnection in the Lower Solar Atmosphere

Song

Zhu

Chen

et al. 2020

ApJL

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White-light flares (WLFs), first observed in 1859, refer to a type of solar flares showing an obvious enhancement of the visible continuum emission. This type of enhancement often occurs in most energetic flares, and is usually interpreted as a consequence of efficient heating in the lower solar atmosphere through non-thermal electrons propagating downward from the energy release site in the corona. However, this coronal-reconnection model has difficulty in explaining the recently discovered small WLFs. Here we report a C2.3 white-light flare, which are associated with several observational phenomena: fast decrease in opposite-polarity photospheric magnetic fluxes, disappearance of two adjacent pores, significant heating of the lower chromosphere, negligible increase of hard X-ray flux, and an associated U-shaped magnetic field configuration. All these suggest that this white-light flare is powered by magnetic reconnection in the lower part of the solar atmosphere rather than by reconnection higher up in the corona.

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Flame-like Ellerman Bombs and Their Connection to Solar Ultraviolet Bursts

Cited by 42 publications

References 49 publications

A Cancellation Nanoflare Model for Solar Chromospheric and Coronal Heating. III. 3D Simulations and Atmospheric Response

A Cancellation Nanoflare Model for Solar Chromospheric and Coronal Heating. III. 3D Simulations and Atmospheric Response

Plasmoid-mediated reconnection in solar UV bursts

A White-light Flare Powered by Magnetic Reconnection in the Lower Solar Atmosphere

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