Probing the Production of Extreme-ultraviolet Late-phase Solar Flares Using the Model Enthalpy-based Thermal Evolution of Loops

Dai, Y.; Ding, M. D.

doi:10.3847/1538-4357/aab898

Cited by 12 publications

(4 citation statements)

References 55 publications

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“…This kind of confined flares has been extensively studied and the strength of the overlying field is thought to be an important factor determining whether a flare is confined (Cheng et al 2011;Nindos et al 2012;Liu et al 2016a;Amari et al 2018). In the event on 2012 July 04, the formations of secondary flare ribbons and late-phase flare loops (Figures 13 and 15) both suggest that the large-scale constraining fields overlying the erupting flux rope are partially reconnected (Sun et al 2013;Dai & Ding 2018). However, the remaining constraining fields that are not reconnecting still hold a high flux ratio compared to the flux rope, hence inhibit the eruption of the flux rope.…”

Section: Discussionmentioning

confidence: 99%

Two Types of Confined Solar Flares

Liu

Hou

et al. 2019

ApJ

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With the aim of understanding the physical mechanisms of confined flares, we selected 18 confined flares during 2011-2017, and classified the confined flares into two types based on their different dynamic properties and magnetic configurations. "Type I" of confined flares are characterized by slipping reconnection, strong shear, and stable filament. "Type II" flares have nearly no slipping reconnection, and have a configuration in potential state after the flare. Filament erupts but is confined by strong strapping field. "Type II" flares could be explained by 2D MHD models while "type I" flares need 3D MHD models. 7 flares of 18 (∼39 %) belong to "type I" and 11 (∼61 %) are "type II" confined flares. The post-flare loops (PFLs) of "type I" flares have a stronger non-potentiality, however, the PFLs in "type II" flares are weakly sheared. All the "type I" flares exhibit the ribbon elongations parallel to the polarity inversion line (PIL) at speeds of several tens of km s −1 . For "type II" flares, only a small proportion shows the ribbon elongations along the PIL. We suggest that different magnetic topologies and reconnection scenarios dictate the distinct properties for the two types of flares. Slipping magnetic reconnections between multiple magnetic systems result in "type I" flares. For "type II" flares, magnetic reconnections occur in anti-parallel magnetic fields underlying the erupting filament. Our study shows that "type I" flares account for more than one third of the overall large confined flares, which should not be neglected in further studies.

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Section: Discussionmentioning

confidence: 99%

Two Types of Confined Solar Flares

Liu

Hou

et al. 2019

ApJ

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“…Nevertheless, our results clearly indicate that, at least for nanoflares, the decay timescales for plasma sampled in cooler SDO/AIA imaging bands are smaller than those found in the hotter channels. Theoretical work is still required to address the specific roles of conductive and radiative cooling in post-flare plasma (e.g., Cargill et al 1995;Dai & Ding 2018), particularly in a regime dominated by small-scale nanoflare events. An important outcome of this work is the fact that a smaller power-law index of ᾱ94 = 1.85 ± 0.02 is estimated for the SDO/AIA 94 Å time series, when compared to ᾱ171 = 1.89±0.01 for the co-spatial and co-temporal 171 Å observations.…”

Section: Discussionmentioning

confidence: 99%

Statistical Signatures of Nanoflare Activity. I. Monte Carlo Simulations and Parameter-space Exploration

Jess

Dillon

Kirk

et al. 2019

ApJ

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Small-scale magnetic reconnection processes, in the form of nanoflares, have become increasingly hypothesized as important mechanisms for the heating of the solar atmosphere, for driving propagating disturbances along magnetic field lines in the Sun's corona, and for instigating rapid jet-like bursts in the chromosphere. Unfortunately, the relatively weak signatures associated with nanoflares places them below the sensitivities of current observational instrumentation. Here, we employ Monte Carlo techniques to synthesize realistic nanoflare intensity time series from a dense grid of power-law indices and decay timescales. Employing statistical techniques, which examine the modeled intensity fluctuations with more than 10 7 discrete measurements, we show how it is possible to extract and quantify nanoflare characteristics throughout the solar atmosphere, even in the presence of significant photon noise. A comparison between the statistical parameters (derived through examination of the associated intensity fluctuation histograms) extracted from the Monte Carlo simulations and SDO/AIA 171Å and 94Å observations of active region NOAA 11366 reveals evidence for a flaring power-law index within the range of 1.82 ≤ α ≤ 1.90, combined with e-folding timescales of 385 ± 26 s and 262 ± 17 s for the SDO/AIA 171Å and 94Å channels, respectively. These results suggest that nanoflare activity is not the dominant heating source for the active region under investigation. This opens the door for future dedicated observational campaigns to not only unequivocally search for the presence of small-scale reconnection in solar and stellar environments, but also quantify key characteristics related to such nanoflare activity.

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“…By comparison, the main flaring loops are significantly shorter (2L∼10-25 Mm), and hence evolve more quickly. In a numerical experiment using the EBTEL model, Dai & Ding (2018) found that with a strong initial loop heating, the hot and warm coronal emissions peak in the conductive cooling and radiative cooling stages, respectively. For the hot coronal emissions, the main flare peak and the late-phase peak temporally overlap because the cooling rate in all loops is very fast during the conductive cooling phase.…”

Section: Discussionmentioning

confidence: 99%

“…By using the model called enthalpy-based thermal evolution of loops (EBTEL; Klimchuk et al 2008;Cargill et al 2012; Barnes et al 2016), Li et al (2014) and Dai & Ding (2018) numerically probed the produc-tion of EUV late-phase flares. In particular, Dai & Ding (2018) found that even with an equal energy partition between the late-phase loop and main flaring loop, the warm coronal late-phase peak is still significantly lower than the corresponding main flare peak. This result may offer a clue as to why EUV late-phase flares are rare among all solar flares.…”

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confidence: 99%

Extremely Large Extreme-ultraviolet Late Phase Powered by Intense Early Heating in a Non-eruptive Solar Flare

Dai

Ding

Zong

et al. 2018

ApJ

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We analyzed and modeled an M1.2 non-eruptive solar flare on 2011 September 9. The flare exhibits a strong late-phase peak of the warm coronal emissions (∼3 MK) of extreme-ultraviolet (EUV), with peak emission over 1.3 times that of the main flare peak. Multiple flare ribbons are observed, whose evolution indicates a two-stage energy release process. A non-linear force-free field (NLFFF) extrapolation reveals the existence of a magnetic null point, a fan-spine structure, and two flux ropes embedded in the fan dome. Magnetic reconnections involved in the flare are driven by the destabilization and rise of one of the flux ropes. In the first stage, the fast ascending flux rope drives reconnections at the null point and the surrounding quasi-separatrix layer (QSL), while in the second stage, reconnection mainly occurs between the two legs of the field lines stretched by the eventually stopped flux rope. The late-phase loops are mainly produced by the first-stage QSL reconnection, while the second-stage reconnection is responsible for the heating of main flaring loops. The first-stage reconnection is believed to be more powerful, leading to an extremely strong EUV late phase. We find that the delayed occurrence of the late-phase peak is mainly due to the long cooling process of the long late-phase loops. Using the model enthalpy-based thermal evolution of loops (EBTEL), we model the EUV emissions from a late-phase loop. The modeling reveals a peak heating rate of 1.1 erg cm −3 s −1 for the late-phase loop, which is obviously higher than previous values.

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Probing the Production of Extreme-ultraviolet Late-phase Solar Flares Using the Model Enthalpy-based Thermal Evolution of Loops

Cited by 12 publications

References 55 publications

Two Types of Confined Solar Flares

Two Types of Confined Solar Flares

Statistical Signatures of Nanoflare Activity. I. Monte Carlo Simulations and Parameter-space Exploration

Extremely Large Extreme-ultraviolet Late Phase Powered by Intense Early Heating in a Non-eruptive Solar Flare

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