Evidence of chromospheric molecular hydrogen emission in a solar flare observed by the <i>IRIS</i> satellite

Mulay, Sargam M.; Fletcher, L.

doi:10.1093/mnras/stab367

Cited by 13 publications

(8 citation statements)

References 29 publications

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“…Significant HXR emissions, produced by non-thermal electrons impacting the lower atmosphere, occur between 12:50 and 13:00 UT, and exhibit multiple bursts with quasi-periodicities between 1 and 2 minutes. Such quasi-periodic pulsations were also observed and studied in EIS, IRIS, and radio spectroscopic observations (Brannon et al 2015;Brosius et al 2016;Karlický et al 2017;Mulay & Fletcher 2021). Five of these bursts are indicated in the figure . Flare energy release is believed to be governed by magnetic reconnection in the corona.…”

Section: Overview Of Observationsmentioning

confidence: 64%

“…EIS and IRIS observations provide spectroscopic diagnostics of flare plasmas at certain locations across some parts of the flare ribbons. The spectroscopic observations were analyzed by Brannon et al (2015), Brosius & Daw (2015), Brosius et al (2016), andMulay &, revealing quasi-periodic pulsations in the time profiles of the intensity and Doppler-shifted upflows and downflows of the plasma.…”

Section: Overview Of Observationsmentioning

confidence: 99%

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Correlated Spatiotemporal Evolution of Extreme-Ultraviolet Ribbons and Hard X-rays in a Solar Flare

Naus,

Qiu,

DeVore

et al. 2021

Preprint

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We analyze the structure and evolution of ribbons from the M7.3 SOL2014-04-18T13 flare using ultraviolet (UV) images from IRIS and SDO/AIA, magnetic data from SDO/HMI, hard X-ray (HXR) images from RHESSI, and light curves from Fermi /GBM, in order to infer properties of coronal magnetic reconnection. As the event progresses, two flare ribbons spread away from the magnetic polarity inversion line. The width of the newly brightened front along the extension of the ribbon is highly intermittent in both space and time, presumably reflecting non-uniformities in the structure and/or dynamics of the flare current sheet. Furthermore, the ribbon width grows most rapidly in regions exhibiting concentrated non-thermal HXR emission, with sharp increases slightly preceding the HXR bursts. The light curve of the ultraviolet emission matches the HXR light curve at photon energies above 25 keV. In other regions the ribbon-width evolution and light curves do not temporally correlate with the HXR emission. This indicates that the production of non-thermal electrons is highly nonuniform within the flare current sheet. Our results suggest a strong connection between the production of non-thermal electrons and the locally enhanced perpendicular extent of flare ribbon fronts, which in turn reflects inhomogeneous structure and/or reconnection dynamics of the current sheet. Despite this variability, the ribbon fronts remain nearly continuous, quasi-one-dimensional features. Thus, although the reconnecting coronal current sheets are highly structured, they remain quasi-two-dimensional and the magnetic energy release occurs systematically, rather than stochastically, through the volume of reconnecting magnetic flux.

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Section: Overview Of Observationsmentioning

confidence: 64%

Section: Overview Of Observationsmentioning

confidence: 99%

Correlated Spatiotemporal Evolution of Extreme-Ultraviolet Ribbons and Hard X-rays in a Solar Flare

Naus,

Qiu,

DeVore

et al. 2021

Preprint

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“…Our inspection of the spectra did not reveal the presence of any identifiable blends to the line, which is in line with other analyses of this line in flares and active regions (e.g., Polito et al 2016b;Doschek et al 2016;Dudík et al 2017;Jeffrey et al 2018;Young et al 2018, to name a few). Mulay & Fletcher (2021) have shown that H 2 line emission can sometimes be detected at flare ribbons, with the 1402.64 Å line blending the Si IV 1402.77 Å line. To rule out the presence of this blend, we inspected the C II spectral window containing the H 2 1333.48 and 1333.80 Å lines analyzed by Mulay & Fletcher (2021) but did not find any traces of these lines.…”

Section: Spectroscopic Analysis Of the Kernelmentioning

confidence: 99%

“…Mulay & Fletcher (2021) have shown that H 2 line emission can sometimes be detected at flare ribbons, with the 1402.64 Å line blending the Si IV 1402.77 Å line. To rule out the presence of this blend, we inspected the C II spectral window containing the H 2 1333.48 and 1333.80 Å lines analyzed by Mulay & Fletcher (2021) but did not find any traces of these lines. This is likely caused by the relatively shorter exposure time of our observations (1 s) compared to the 8 s exposure time used in the data set they analyzed.…”

Section: Spectroscopic Analysis Of the Kernelmentioning

confidence: 99%

Blueshifted Si iv 1402.77 Å Line Profiles in a Moving Flare Kernel Observed by IRIS

Lörinčík

Dudík

Polito

2022

ApJ

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We analyze the spectra of a slipping flare kernel observed during the 2015 June 22 M6.5-class flare by the Interface Region Imaging Spectrograph (IRIS). During the impulsive and peak phases of the flare, loops exhibiting an apparent slipping motion along the ribbons were observed in the 131 Å channel of SDO/AIA. The IRIS spectrograph slit observed a portion of the ribbons, including a moving kernel corresponding to a flare loop footpoint in Si iv, C ii, and Mg ii at a very-high 1 s cadence. The spectra observed in the kernel were mostly redshifted and exhibited pronounced red wings, as typically observed in large flares. However, in a small region in one of the ribbons, the Si iv 1402.77 Å line was partially blueshifted, with the corresponding Doppler velocity ∣v D∣ exceeding 50 km s−1. In the same region, the C ii 1334.53, 1335.66, and 1335.71 Å lines were weakly blueshifted (∣v D∣ < 20 km s−1) and showed pronounced blue wings, which were also observed in the Mg ii k 2796.35 Å as well as the Mg ii triplet 2798.75 and 2798.82 Å lines. Using high-cadence AIA observations we found that the region where the blueshifts occurred corresponds to the accelerating kernel front as it moved through a weak field region. The IRIS observations with high resolution allowed us to capture the acceleration of the kernel under the slit for the first time. The unique observations of blueshifted chromospheric and TR lines provide new constraints for current models of flares.

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“…Our inspection of the spectra did not reveal the presence of any identifiable blends to the line, which is in line with other analyzes of this line in flares and active regions (e.g., Doschek et al 2016;Polito et al 2016b;Dudík et al 2017;Jeffrey et al 2018;Young et al 2018, to name a few). Mulay & Fletcher (2021) have shown that H 2 line emission can sometimes be detected at flare ribbons, with the 1402.64 Å line blending the Si IV 1402.77 Å line. To rule out the presence of this blend, we inspected the C II spectral window containing the H 2 1333.48 Å and 1333.80 Å lines analyzed by Mulay & Fletcher (2021) but did not find any traces of these lines.…”

Section: Spectroscopic Analysis Of the Kernelmentioning

confidence: 99%

Blueshifted Si IV 1402.77Å line profiles in a moving flare kernel observed by IRIS

Lörinčík¹,

Dudík²,

Polito³

2022

Preprint

View full text Add to dashboard Cite

We analyze spectra of a slipping flare kernel observed during the 2015 June 22 M6.5-class flare by the Interface Region Imaging Spectrograph (IRIS). During the impulsive and peak phases of the flare, loops exhibiting an apparent slipping motion along the ribbons were observed in the 131 Å channel of SDO/AIA. The IRIS spectrograph slit observed a portion of the ribbons, including a moving kernel corresponding to a flare loop footpoint in Si IV, C II, and Mg II at a very-high 1 s cadence. The spectra observed in the kernel were mostly redshifted and exhibited pronounced red wings, as typically observed in large flares. However, in a small region in one of the ribbons, the Si IV 1402.77 Å line was partially blueshifted, with the corresponding Doppler velocity |v D | exceeding 50 km s −1 . In the same region, the C II 1334.53 Å, 1335.66 Å and 1335.71 Å lines were weakly blueshifted (|v D | < 20 km s −1 ) and showed pronounced blue wings, which were observed also in the Mg II k 2796.35 Å as well as the Mg II triplet 2798.75 Å and 2798.82 Å lines. Using high-cadence AIA observations we found that the region where the blueshifts occurred corresponds to the accelerating kernel front as it moved through a weak-field region. The IRIS observations with high resolution allowed us to capture the acceleration of the kernel under the slit for the first time. The unique observations of blueshifted chromospheric and TR lines provide new constrains for current models of flares.

show abstract

Evidence of chromospheric molecular hydrogen emission in a solar flare observed by the IRIS satellite

Cited by 13 publications

References 29 publications

Correlated Spatiotemporal Evolution of Extreme-Ultraviolet Ribbons and Hard X-rays in a Solar Flare

Correlated Spatiotemporal Evolution of Extreme-Ultraviolet Ribbons and Hard X-rays in a Solar Flare

Blueshifted Si iv 1402.77 Å Line Profiles in a Moving Flare Kernel Observed by IRIS

Blueshifted Si IV 1402.77Å line profiles in a moving flare kernel observed by IRIS

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