Suppression of Hydrogen Emission in an X-class White-light Solar Flare

Prochazka, Ondrej; Milligan, Ryan O.; Allred, Joel C.; Kowalski, Adam F.; Kotrč, P.; Mathioudakis, M.

doi:10.3847/1538-4357/aa5da8

Cited by 12 publications

(20 citation statements)

References 44 publications

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“…Any systematic rise both redward and blueward of the Balmer jump was not detected during the impulsive phase (Figure 1(e)). It should be noted that the IS spectrum shown in Figure 1(e) is different from those presented in Procházka et al (2017), as, in this work, the reference preflare spectrum was taken much closer to the flare onset …”

Section: The X1 Flare On 2014 June 11: Observations and Data Analysismentioning

confidence: 81%

“…The location of the deepest penetration coincides with the peak in the contribution function of the Balmer continuum (Kennedy et al 2015). Procházka et al (2017) reported the observation of an X1 WLF that was observed at the Ondrějov Observatory, Czech Republic, with the Image Selector (IS, Kotrč et al 2016) instrument, providing rare optical spectra (spectral resolution ∼0.03 nm per pixel) in conjunction with modern space-based instruments. The authors reported no emission in the higher order Balmer lines, as well as weak emission in Lyman lines and Lyman continuum (LyC).…”

Section: Introductionmentioning

confidence: 81%

“…Procházka et al 2017). We were only able to reliably determine a lower limit of the WL contrast in the observations due the large temporal and spatial variations in the active region (Figure 1(a)).…”

Section: White Light From Sdo/hmi Observationsmentioning

confidence: 90%

“…In this paper, we carry out a more detailed analysis of electron and proton beam heating models in order to explain the observations of the type II WLF presented by Procházka et al (2017). In Section 2, we provide an outline of the data sets obtained from both ground-and space-based instruments.…”

Section: Introductionmentioning

confidence: 99%

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Reproducing Type II White-light Solar Flare Observations with Electron and Proton Beam Simulations

Prochazka

Reid

Milligan

et al. 2018

ApJ

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We investigate the cause of the suppressed Balmer series and the origin of the white-light continuum emission in the X1.0 class solar flare on 2014 June 11. We use radiative hydrodynamic simulations to model the response of the flaring atmosphere to both electron and proton beams, which are energetically constrained using Ramaty High Energy Solar Spectroscopic Imager and Fermi observations. A comparison of synthetic spectra with the observations allows us to narrow the range of beam fluxes and low energy cutoff that may be applicable to this event. We conclude that the electron and proton beams that can reproduce the observed spectral features are those that have relatively low fluxes and high values for the low energy cutoff. While electron beams shift the upper chromosphere and transition region to greater geometrical heights, proton beams with a similar flux leave these areas of the atmosphere relatively undisturbed. It is easier for proton beams to penetrate to the deeper layers and not deposit their energy in the upper chromosphere where the Balmer lines are formed. The relatively weak particle beams that are applicable to this flare do not cause a significant shift of the τ=1 surface and the observed excess WL emission is optically thin.

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Section: The X1 Flare On 2014 June 11: Observations and Data Analysismentioning

confidence: 81%

Section: Introductionmentioning

confidence: 81%

Section: White Light From Sdo/hmi Observationsmentioning

confidence: 90%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Reproducing Type II White-light Solar Flare Observations with Electron and Proton Beam Simulations

Prochazka

Reid

Milligan

et al. 2018

ApJ

Self Cite

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“…However, chromospheric condensations (Livshits et al 1981;Fisher 1989;Kowalski et al 2015b) with low continuum optical depth also produce broadband continuum radiation with a large jump in flux near the hydrogen Balmer limit (Gan et al 1992;Kowalski et al 2017a). The capability to test model predictions of the Balmer jump in solar flares has largely disappeared, which is unfortunate because spectra of solar flares in the 1980s (primarily from the Universal Spectrograph) exhibit a variety of characteristics in the Balmer jump spectral region (Hiei 1982;Acampa et al 1982;Neidig 1983;Donati-Falchi et al 1984Boyer et al 1985;Kowalski et al 2015a;Procházka et al 2017), and we now have methods to model opacity from blended lines and dissolved levels (Uitenbroek 2001;Kowalski et al 2015b). Therefore, we must employ other spectral diagnostics that critically test these models and constrain whether the white-light results from photospheric heating, as suggested by a recent off-limb measurement of the emission height (Martínez Oliveros et al 2012, but see Battaglia & Kontar (2011) and Krucker et al (2015)), primarily from chromospheric heating, or significant heating throughout several layers of the lower atmosphere (Neidig et al 1993a,b;Kleint et al 2016).…”

Section: Introductionmentioning

confidence: 99%

Spectral Evidence for Heating at Large Column Mass in Umbral Solar Flare Kernels. I. IRIS Near-UV Spectra of the X1 Solar Flare of 2014 October 25

Kowalski

Butler²,

Daw

et al. 2019

ApJ

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The GOES X1 flare SOL2014-10-25T17:08:00 was a three-ribbon solar flare observed with IRIS in the near and far ultraviolet. One of the flare ribbons crossed a sunspot umbra, producing a dramatic, ∼ 1000% increase in the nearultraviolet (NUV) continuum radiation. We comprehensively analyze the ultraviolet spectral data of the umbral flare brightenings, which provide new challenges for radiative-hydrodynamic modeling of the chromospheric velocity field and the white-light continuum radiation. The emission line profiles in the umbral flare brightenings exhibit redshifts and profile asymmetries, but these are significantly smaller than in another, well-studied X-class solar flare. We present a ratio of the NUV continuum intensity to the Fe II λ2814.45 intensity. This continuum-to-line ratio is a new spectral diagnostic of significant heating at high column mass (log m/[g cm −2 ] > −2) during solar flares because the continuum and emission line radiation originate from relatively similar temperatures but moderately different optical depths. The full spectral readout of these IRIS data also allow for a comprehensive survey of the flaring NUV landscape: in addition to many lines of Fe II and Cr II, we identify a new solar flare emission line, He I λ2829.91 (as previously identified in laboratory and early-type stellar spectra). The Fermi/GBM hard X-ray data provide inputs to radiative-hydrodynamic models (which will be presented in Paper II) in order to better understand the large continuum-to-line ratios, the origin of the white-light continuum radiation, and the role of electron beam heating in the low atmosphere.adam.f.kowalski@colorado.edu 1 Various loose definitions of a "white-light flare" exist, including a flare that could be detected by the eye (which is broadband). In dMe stars, U -band flares are certainly considered white-light flares even though our eye is not sensitive to these wavelengths, and flares detected in a narrow passband of SDO/HMI are often called white-light flares, assuming that continuum radiation is the source of the HMI increase. Generally, a white-light flare is a flare that produces a change in continuum radiation that could be detected in the Johnson U and/or V bands.

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Sunquake with a second bounce, other sunquakes, and emission associated with the X9.3 flare of 6 September 2017

Zharkov

Matthews²,

Zharkova

et al. 2020

A&A

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Aims. The 6 September 2017 X9.3 solar flare produced very unique observations of magnetic field transients and a few seismic responses, or sunquakes, detected by the Helioseismic and Magnetic Imager (HMI) instrument aboard Solar Dynamic Observatory (SDO) spacecraft, including the strongest sunquake ever reported. This flare was one of a few flares occurring within a few days or hours in the same active region. Despite numerous reports of the fast variations of magnetic field, and seismic and white light emission, no attempts were made to interpret the flare features using multi-wavelength observations. In this study, we attempt to produce the summary of available observations of the most powerful flare of the 6 September 2017 obtained using instruments with different spatial resolutions (this paper) and to provide possible interpretation of the flaring events, which occurred in the locations of some seismic sources (a companion Paper II). Methods. We employed non-linear force-free field extrapolations followed by magnetohydrodynamic simulations in order to identify the presence of several magnetic flux ropes prior to the initiation of this X9.3 flare. Sunquakes were observed using the directional holography and time–distance diagram detection techniques. The high-resolution method to detect the Hα line kernels in the CRISP instrument at the diffraction level limit was also applied. Results. We explore the available γ-ray (GR), hard X-ray (HXR), Lyman-α, and extreme ultra-violet (EUV) emission for this flare comprising two flaring events observed by space- and ground-based instruments with different spatial resolutions. For each flaring event we detect a few seismic sources, or sunquakes, using Dopplergrams from the HMI/SDO instrument coinciding with the kernels of Hα line emission with strong redshifts and white light sources. The properties of sunquakes were explored simultaneously with the observations of HXR (with KONUS/WIND and the Reuven Ramaty High Energy Solar Spectroscopic Imager payload), EUV (with the Atmospheric Imaging Assembly (AIA/SDO and the EUV Imaging Spectrometer aboard Hinode payload), Hα line emission (with the CRisp Imaging Spectro-Polarimeter (CRISP) in the Swedish Solar Telescope), and white light emission (with HMI/SDO). The locations of sunquake and Hα kernels are associated with the footpoints of magnetic flux ropes formed immediately before the X9.3 flare onset. Conclusions. For the first time we present the detection of the largest sunquake ever recorded with the first and second bounces of acoustic waves generated in the solar interior, the ripples of which appear at a short distance of 5–8 Mm from the initial flare location. Four other sunquakes were also detected, one of which is likely to have occurred 10 min later in the same location as the largest sunquake. Possible parameters of flaring atmospheres in the locations with sunquakes are discussed using available temporal and spatial coverage of hard X-ray, GR, EUV, hydrogen Hα-line, and white light emission in preparation for their use in an interpretation to be given in Paper II.

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Suppression of Hydrogen Emission in an X-class White-light Solar Flare

Cited by 12 publications

References 44 publications

Reproducing Type II White-light Solar Flare Observations with Electron and Proton Beam Simulations

Reproducing Type II White-light Solar Flare Observations with Electron and Proton Beam Simulations

Spectral Evidence for Heating at Large Column Mass in Umbral Solar Flare Kernels. I. IRIS Near-UV Spectra of the X1 Solar Flare of 2014 October 25

Sunquake with a second bounce, other sunquakes, and emission associated with the X9.3 flare of 6 September 2017

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