Multiwavelength Observations of a B-class Flare Using XSM, AIA, and XRT

Rao, Yamini K.; Mondal, B.; Del Zanna, Giulio; Mithun, N. P. S.; Vadawale, S. V.; Reeves, K. K.; Mason, Helen E.; Bhardwaj, Anil

doi:10.3847/1538-4357/acf46a

Cited by 3 publications

(2 citation statements)

References 24 publications

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“…These abundances are used to calculate the bolometric radiative loss rate that directly impacts the cooling of the plasma. Many recent X-ray observations of flares, however, clearly show that elemental abundances are not fixed and vary with time over the duration of the flare (Del Zanna et al 2021;Mondal et al 2021;Mithun et al 2022;Kepa et al 2023;Nama et al 2023;Rao et al 2023;Suarez & Moore 2023;Woods et al 2023). Similar observations have also found that the abundances of active regions (ARs) vary relatively quickly as well (Mondal et al 2023).…”

Section: Introductionmentioning

confidence: 91%

Modeling Time-variable Elemental Abundances in Coronal Loop Simulations

Reep,

Unverferth,

Barnes

et al. 2024

ApJL

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Numerous recent X-ray observations of coronal loops in both active regions and solar flares have shown clearly that elemental abundances vary with time. Over the course of a flare, they have been found to move from coronal values toward photospheric values near the flare peak, before slowly returning to coronal values during the gradual phase. Coronal loop models typically assume that the elemental abundances are fixed, however. In this work, we introduce a time-variable abundance factor into the 0D ebtel++ code that models the changes due to chromospheric evaporation in order to understand how this affects coronal loop cooling. We find that for strong heating events (≳1 erg s−1 cm−3), the abundances quickly tend towards photospheric values. For smaller heating rates, the abundances fall somewhere between coronal and photospheric values, causing the loop to cool more quickly than the time-fixed photospheric cases (typical flare simulations) and more slowly than time-fixed coronal cases (typical AR simulations). This suggests heating rates in quiescent AR loops no larger than ≈0.1 erg s−1 cm−3 to be consistent with recent measurements of abundance factors f ≳ 2.

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Section: Introductionmentioning

confidence: 91%

Modeling Time-variable Elemental Abundances in Coronal Loop Simulations

Reep,

Unverferth,

Barnes

et al. 2024

ApJL

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“…A change from coronal-to photospheric-like elemental abundances has sometimes been observed in flares, including microflares of similar brightness to these events (e.g., Rao et al 2023). In addition to the Bremsstrahlung continuum, NuSTAR has sensitivity to spectral lines from elements with low first ionization potential, which are comparatively less abundant in the photosphere.…”

Section: Variable-temperature-range Demsmentioning

confidence: 99%

Thermal Evolution of an Active Region Through Quiet and Flaring Phases as Observed by NuSTAR, XRT, and AIA

Duncan,

Masek,

Shih

et al. 2024

ApJ

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Solar active regions (ARs) contain a broad range of temperatures, with the thermal plasma distribution often observed to peak in the few millions of kelvin. Differential emission measure (DEM) analysis can allow instruments with diverse temperature responses to be used in concert to estimate this distribution. Nuclear Spectroscopic Telescope ARray (NuSTAR) hard X-ray (HXR) observations are uniquely sensitive to the highest-temperature components of the corona, and thus extremely powerful for examining signatures of reconnection-driven heating. Here, we use NuSTAR diagnostics in combination with extreme-ultraviolet and soft X-ray observations (from the Solar Dynamics Observatory/Atmospheric Imaging Assembly and Hinode/X-Ray Telescope) to construct DEMs over 170 distinct time intervals during a 5 hr observation of an alternately flaring and quiet active region (NOAA designation AR 12712). This represents the first HXR study to examine the time evolution of the distribution of thermal plasma in an AR. During microflares, we find that the initial microflare-associated plasma heating is predominantly heating of material that is already relatively hot, followed later on by broader heating of initially cooler material. During quiescent times, we show that the amount of extremely hot (>10 MK) material in this region is significantly (∼2–4 orders of magnitude) less than that found in the quiescent AR observed in HXRs by FOXSI-2. This result implies there can be radically different high-temperature thermal distributions in different ARs, and strongly motivates future HXR DEM studies covering a large number of these regions.

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Spatially resolved plasma composition evolution in a solar flare – The effect of reconnection outflow

To,

Brooks,

Imada

et al. 2024

A&A

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Solar flares exhibit complex variations in elemental abundances compared to photospheric values. These abundance variations, characterized by the first ionization potential (FIP) bias, remain challenging to interpret. We aim to 1) examine the spatial and temporal evolution of coronal abundances in the X8.2 flare on 2017 September 10, and 2) provide a new scenario to interpret the often observed high FIP bias loop top, and provide further insight into differences between spatially resolved and Sun-as-a-star flare composition measurements. We analyzed 12 Hinode/Extreme-ultraviolet Imaging Spectrometer (EIS) raster scans spanning 3.5 hours, employing both Ca XIV Ar XIV and Fe XVI S XIII composition diagnostics to derive FIP bias values. We used the Markov Chain Monte Carlo (MCMC) differential emission measure (DEM) method to obtain the distribution of plasma temperatures, which forms the basis for the FIP bias calculations. Both the Ca/Ar and Fe/S composition diagnostics consistently show that flare loop tops maintain high FIP bias values of $>$2--6, with peak phase values exceeding 4, over the extended duration, while footpoints exhibit photospheric FIP bias of sim 1. The consistency between these two diagnostics forms the basis for our interpretation of the abundance variations. We propose that this variation arises from a combination of two distinct processes: high FIP bias plasma downflows from the plasma sheet confined to loop tops, and chromospheric evaporation filling the loop footpoints with low FIP bias plasma. Mixing between these two sources produces the observed gradient. Our observations show that the localized high FIP bias signature at loop tops is likely diluted by the bright footpoint emission in spatially averaged measurements. The spatially resolved spectroscopic observations enabled by EIS prove critical for revealing this complex abundance variation in loops. Furthermore, our observations show clear evidence that the origin of hot flare plasma in flaring loops consists of a combination of both directly heated plasma in the corona and from ablated chromospheric material; and our results provide valuable insights into the formation and composition of loop top brightenings, also known as EUV knots, which are a common feature at the tops of flare loops.

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Multiwavelength Observations of a B-class Flare Using XSM, AIA, and XRT

Cited by 3 publications

References 24 publications

Modeling Time-variable Elemental Abundances in Coronal Loop Simulations

Modeling Time-variable Elemental Abundances in Coronal Loop Simulations

Thermal Evolution of an Active Region Through Quiet and Flaring Phases as Observed by NuSTAR, XRT, and AIA

Spatially resolved plasma composition evolution in a solar flare – The effect of reconnection outflow

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