RADYN Simulations of Non-thermal and Thermal Models of Ellerman Bombs

Hong, Jie; Carlsson, Mats; Ding, M. D.

doi:10.3847/1538-4357/aa80e3

Cited by 27 publications

(28 citation statements)

References 59 publications

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“…2. For cases FQa and FQb, we see a dimming in both the line and the nearby continuum during the first 2 s. The dimming effect caused by non-thermal electrons seems a common phenomenon in flares and Ellerman bombs, which has already been reported in some previous simulations (Abbett & Hawley 1999;Allred et al 2006;Hong et al 2017). Dimming in this line is also seen in the calculation results of Sharykin et al (2017).…”

Section: Introductionsupporting

confidence: 86%

“…We assume an atmosphere in a 10 Mm quarter-circular loop structure. Following Hong et al (2017), we employ two different atmospheric models to construct the initial atmosphere. One is a quiet-Sun atmosphere, the same as in Hong et al (2017), which is based on the VAL3C model (Vernazza et al 1981); the other is a penumbral atmosphere that is based on the semi-empirical model of Ding & Fang (1989).…”

Section: Introductionmentioning

confidence: 99%

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Non-LTE Calculations of the Fe i 6173 Å Line in a Flaring Atmosphere

Hong

Ding

et al. 2018

ApJL

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The Fe I 6173 Å line is widely used in the measurements of vector magnetic fields by instruments including the Helioseismic and Magnetic Imager (HMI). We perform non-local thermodynamic equilibrium calculations of this line based on radiative hydrodynamic simulations in a flaring atmosphere. We employ both a quiet-Sun atmosphere and a penumbral atmosphere as the initial one in our simulations. We find that, in the quiet-Sun atmosphere, the line center is obviously enhanced during an intermediate flare. The enhanced emission is contributed from both radiative backwarming in the photosphere and particle beam heating in the lower chromosphere. A blue asymmetry of the line profile also appears due to an upward mass motion in the lower chromosphere. If we take a penumbral atmosphere as the initial atmosphere, the line has a more significant response to the flare heating, showing a central emission and an obvious asymmetry. The low spectral resolution of HMI would indicate some loss of information but the enhancement and line asymmetry are still kept. By calculating polarized line profiles, we find that the Stokes I and V profiles can be altered as a result of flare heating. Thus the distortion of this line has a crucial influence on the magnetic field measured from this line, and one should be cautious in interpreting the magnetic transients observed frequently in solar flares.

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Section: Introductionsupporting

confidence: 86%

Section: Introductionmentioning

confidence: 99%

Non-LTE Calculations of the Fe i 6173 Å Line in a Flaring Atmosphere

Hong

Ding

et al. 2018

ApJL

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“…More recently, Reid et al (2017) and Hong et al (2017) used the radiative hydrodynamics code RADYN to model Ellerman bombs and found that temperature enhancements of up to ∆T =3000 K yielded Hα and Ca ii 8542 Å profiles similar to observations. Both studies also considered Mg ii k, where a larger energy deposition was required to obtain profile shapes similar to the observations, however, simultaneous agreement between all three diagnostics could not be achieved in either of those studies.…”

Section: Temperature Stratificationmentioning

confidence: 79%

Dissecting bombs and bursts: non-LTE inversions of low-atmosphere reconnection in SST and IRIS observations

Vissers

Rodríguez

Libbrecht

et al. 2019

A&A

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Ellerman bombs and UV bursts are transient brightenings that are ubiquitously observed in the lower atmospheres of active and emerging flux regions. As they are believed to pinpoint sites of magnetic reconnection in reconfiguring fields, understanding their occurrence and detailed evolution may provide useful insights in the overall evolution of active regions. Here we present results from inversions of SST/CRISP and CHROMIS, as well as IRIS data of such transient events. Combining information from the Mg ii & k, Si iv and Ca ii 8542 Å and Ca ii H & K lines, we aim to characterise their temperature and velocity stratification, as well as their magnetic field configuration. We find average temperature enhancements of a few thousand kelvin close to the classical temperature minimum, similar to previous studies, but localised peak temperatures of up to 10,000-15,000 K from Ca ii inversions. Including Mg ii appears to generally dampen these temperature enhancements to below 8000 K, while Si iv requires temperatures in excess of 10,000 K at low heights, but may also be reproduced with secondary temperature enhancements of 35,000-60,000 K higher up. However, reproducing Si iv comes at the expense of overestimating the Mg ii emission. The line-of-sight velocity maps show clear bi-directional jet signatures for some events and strong correlation with substructure in the intensity images in general. Absolute lineof-sight velocities range between 5-20 km s −1 on average, with slightly larger velocities towards the observer than away. The inverted magnetic field parameters show an enhancement of the horizontal field co-located with the brightenings at heights similar to that of the temperature increase. We are thus able to largely reproduce the observational properties of Ellerman bombs with UV burst signature (e.g. intensities, profile asymmetries, morphology and bi-directional jet signatures) with temperature stratifications peaking close to the classical temperature minimum. Correctly modelling the Si iv emission in agreement with all other diagnostics is, however, an outstanding issue and remains paramount in explaining its apparent coincidence with Hα emission. Fine-tuning the approach (accounting for resolution differences, fitting localised temperature enhancements and/or performing spatially-coupled inversions) is likely necessary in order to obtain better agreement between all considered diagnostics.

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“…The discovery of IBs led Fang et al (2017), and Hong et al (2017a) to investigate whether the EB models could be modified to produce Si IV emission. Fang et al (2017) considered temperatures of the hot component up to 15 kK, but then the chromospheric signatures were not consistent with the EB observations.…”

Section: Uv Burst Modelingmentioning

confidence: 99%

Solar Ultraviolet Bursts

et al. 2018

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The term "ultraviolet (UV) burst" is introduced to describe small, intense, transient brightenings in ultraviolet images of solar active regions. We inventorize their properties and provide a definition based on image sequences in transition-region lines. Coronal signatures are rare, and most bursts are associated with small-scale, canceling oppositepolarity fields in the photosphere that occur in emerging flux regions, moving magnetic features in sunspot moats, and sunspot light bridges. We also compare UV bursts with similar transition-region phenomena found previously in solar ultraviolet spectrometry and with similar phenomena at optical wavelengths, in particular Ellerman bombs. Akin to the lat-Electronic supplementary material The online version of this article (https://doi.

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RADYN Simulations of Non-thermal and Thermal Models of Ellerman Bombs

Cited by 27 publications

References 59 publications

Non-LTE Calculations of the Fe i 6173 Å Line in a Flaring Atmosphere

Non-LTE Calculations of the Fe i 6173 Å Line in a Flaring Atmosphere

Dissecting bombs and bursts: non-LTE inversions of low-atmosphere reconnection in SST and IRIS observations

Solar Ultraviolet Bursts

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