The Chromospheric Response to the Sunquake Generated by the X9.3 Flare of NOAA 12673

Quinn, S.; Reid, Aaron; Mathioudakis, M.; Nelson, C. J.; Prasad, S. Krishna; Zharkov, S.

doi:10.3847/1538-4357/ab2c9e

Cited by 15 publications

(19 citation statements)

References 37 publications

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“…The resulting waves could produce ripples with much greater bounce heights than the usual 3 km (Kosovichev & Zharkova 1998), approaching the chromosphere. These could be seen as ripples in Ca II spectrograms occurring in the chromosphere reported for this flare by Quinn et al (2019) in SST data as was suggested for the similar observations of ripples in Ca II emission by Hinode (Kosovichev 2011).…”

Section: Detection With the Time-distance Diagramsupporting

confidence: 84%

“…Further helioseismic analyses of magneto-acoustic waves in this active region were carried by ?, who also discovered fast and slow magnetoacoustic waves that occurred prior to the major sunquakes and travelled through this active region. Similar waves were also seen in Ca II line spectral observations by the Swedish Solar Telescope (SST), as recently reported by Quinn et al (2019), who linked these Ca II waves to the largest sunquake. Keeping in mind that maximum Doppler velocities of the first bounce of these acoustic waves formed in the interior measured from the HMI dopplergrams do not exceed of ±3 km/s at the photosphere as reported in Fig.…”

Section: Introductionsupporting

confidence: 83%

“…??, top panels) with a cadence of 15 seconds. The reduction and processing of this data was carried out by the group at the Queens University Belfast (Quinn et al 2019) using the general procedures for the reduction of CRISP data (see their methods section in Druett et al 2017).…”

Section: Images Of Hα-sources With Redshiftsmentioning

confidence: 99%

“…Keeping in mind that maximum Doppler velocities of the first bounce of these acoustic waves formed in the interior measured from the HMI dopplergrams do not exceed of ±3 km/s at the photosphere as reported in Fig. 2 by Sharykin & Kosovichev (2018), it is important to establish, whether these or other waves can reach the heights of the chromosphere to produce the Ca II waves seen by Quinn et al (2019). Alternatively, these chromospheric Ca II waves may be linked to the slow magnetoacoustic waves seen in the HMI dopplergrams prior the sunquake onsets as reported by ?.…”

Section: Introductionmentioning

confidence: 98%

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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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Section: Detection With the Time-distance Diagramsupporting

confidence: 84%

Section: Introductionsupporting

confidence: 83%

Section: Images Of Hα-sources With Redshiftsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

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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

Self Cite

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“…It is likely that the ripples generated by this hypothetical seismic source 5 can be interfering with the ripples from this seismic source 2 generated before in the same location. These acoustic waves can have a resonant interference once suggested for the similar seismic events seen in Ca II dopplergrams by Hinode (Kosovichev 2011), thus producing the unusual seismic waves observed in Ca II emission in the chromosphere (Quinn et al 2019).…”

Section: Observed Properties Of the Sunquakesmentioning

confidence: 59%

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

Zharkova

Zharkov

Druett

et al. 2020

A&A

Self Cite

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In this paper we present the interpretation of the observations of the flare from 6 September 2017 reported in Paper I. These include gamma-ray (GR), hard X-ray (HXR), soft X-rays, Lyα line, extreme ultraviolet (EUV), Hα, and white light (WL) emission, which were recorded during the two flaring events 1 (FE1) and 2 (FE2) that occurred at 11:55:37 UT (FE1) and 12:06:40 UT (FE2). Paper I also reported the first detection of the sunquake with first and second bounces of seismic waves combined with four other sunquakes in different locations supported with the observations of HXR, GR, EUV, Hα, and WL emission with strongly varying spatial resolution and temporal coverage. In the current paper, we propose some likely scenarios for heating of flaring atmospheres in the footpoints with sunquakes which were supported with EUV and Hα emission. We used a range of parameters derived from the HXR, EUV, and Hα line observations to generate hydrodynamic models, which can account for the blueshifts derived from the EUV emission and the redshifts observed with the EUV Imaging Spectrometer in the He II line and by the CRisp Imaging Spectro-Polarimeter in the Swedish Solar Telescope in Hα line emission. The parameters of hydrodynamic shocks produced by different beams in flaring atmospheres were used as the initial conditions for another type of hydrodynamic models that were developed for acoustic wave propagation in the solar interior. These models simulate the sets of acoustic waves produced in the interior by the hydrodynamic shocks from atmospheres above deposited in different footpoints of magnetic loops. The Hα line profiles with large redshifts in three kernels (two in FE1 and one in FE2) were interpreted with the full non-local thermodynamic equilibrium radiative simulations in all optically thick transitions (Lyman lines and continuum Hα, Hβ, and Pα) applied for flaring atmospheres with fast downward motions while considering thermal and non-thermal excitation and ionisation of hydrogen atoms by energetic power-law electron beams. The observed Hα line profiles in three kernels were fit with the simulate blue wing emission of the Hα line profiles shifted significantly (by 4–6 Å) towards the line red wings, because of strong downward motions with velocities about 300 km s−1 by the shocks generated in flaring atmospheres by powerful beams. The flaring atmosphere associated with the largest sunquake (seismic source 2 in FE1) is found consistent with being induced by a strong hydrodynamic shock produced by a mixed beam deposited at an angle of −30° from the local vertical. We explain the occurrence of a second bounce in the largest sunquake by a stronger momentum delivered by the shock generated in the flaring atmosphere by a mixed beam and deeper depths of the interior where this shock was deposited. Indeed, the shock with mixed beam parameters is found deposited deeply into the interior beneath the flaring atmosphere under the angle to the local vertical that would allow the acoustic waves generated in the direction closer to the surface to conserve enough energy for the second bounces from the interior layers and from the photosphere. The wave characteristics of seismic sources 1 and 3 (in FE1) were consistent with those produced by the shocks generated by similar mixed beams deposited at the angles −(0 − 10)° (seismic source 1) and +30° (seismic source 3) to the local vertical. The differences of seismic signatures produced in the flares of 6 September 2011 and 2017 are also discussed.

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Non-LTE inversions of a confined X2.2 flare

Vissers

Danilović

Rodríguez

et al. 2020

A&A

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Context. Obtaining an accurate measurement of magnetic field vector in the solar atmosphere is essential for studying changes in field topology during flares and reliably modelling space weather. Aims. We tackle this problem by applying various inversion methods to a confined X2.2 flare that occurred in NOAA AR 12673 on 6 September 2017 and comparing the photospheric and chromospheric magnetic field vector with the results of two numerical models of this event. Methods. We obtained the photospheric magnetic field from Milne-Eddington and (non-)local thermal equilibrium (non-LTE) inversions of Hinode SOT/SP Fe I 6301.5 Å and 6302.5 Å. The chromospheric field was obtained from a spatially regularised weak-field approximation (WFA) and non-LTE inversions of Ca II 8542 Å observed with CRISP at the Swedish 1 m Solar Telescope. We investigated the field strengths and photosphere-to-chromosphere shear in the field vector. Results. The LTE- and non-LTE-inferred photospheric magnetic field components are strongly correlated across several optical depths in the atmosphere, with a tendency towards a stronger field and higher temperatures in the non-LTE inversions. For the chromospheric field, the non-LTE inversions correlate well with the spatially regularised WFA, especially in terms of the line-of-sight field strength and field vector orientation. The photosphere exhibits coherent strong-field patches of over 4.5 kG, co-located with similar concentrations exceeding 3 kG in the chromosphere. The obtained field strengths are up to two to three times higher than in the numerical models, while the photosphere-to-chromosphere shear close to the polarity inversion line is more concentrated and structured. Conclusions. In the photosphere, the assumption of LTE for Fe I line formation does not yield significantly different magnetic field results in comparison to the non-LTE case, while Milne-Eddington inversions fail to reproduce the magnetic field vector orientation where Fe I is in emission. In the chromosphere, the non-LTE-inferred field is excellently approximated by the spatially regularised WFA. Our inversions confirm the locations of flux rope footpoints that have been predicted by numerical models. However, pre-processing and lower spatial resolution lead to weaker and smoother field in the models than what our data indicate. This highlights the need for higher spatial resolution in the models to better constrain pre-eruptive flux ropes.

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The Chromospheric Response to the Sunquake Generated by the X9.3 Flare of NOAA 12673

Cited by 15 publications

References 37 publications

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

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

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

Non-LTE inversions of a confined X2.2 flare

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