Observations of the Quiet Sun during the Deepest Solar Minimum of the Past Century with Chandrayaan-2 XSM: Elemental Abundances in the Quiescent Corona

Vadawale, S.; Mondal, Biswajit; Mithun, N. P. S.; Sarkar, Aveek; Janardhan, P.; Joshi, Bhuwan; Bhardwaj, Anil; Shanmugam, M.; Patel, Alkesh B.; Adalja, Hitesh Kumar L.; Goyal, Subhash; Ladiya, Tinkal; Tiwari, Neeraj K.; Singh, Nishant K.; Kumar, Sushil

doi:10.3847/2041-8213/abf35d

Cited by 21 publications

(40 citation statements)

References 44 publications

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“…For soft X-ray flares, data are now available from highresolution crystal spectrometers such as the Rentgenovsky Spekrometr s Izognutymi Kristalami (RESIK) instrument on the CORONAS-F spacecraft (wavelength range 3-6 Å, operational 2001-2003: Sylwester et al 2005 and broadband spectrometers with spectral resolution between about 100-200 eV (Narendranath et al 2014;Caspi et al 2015;Katsuda et al 2020;Vadawale et al 2021) and 0.6-1 keV (at 6 keV; Phillips & Dennis 2012;Dennis et al 2015). The RESIK and broadband spectrometers viewed the flare continuum, so absolute abundances can be inferred from line-tocontinuum ratios.…”

Section: Introductionmentioning

confidence: 99%

New Solar Flare Calcium Abundances with No Surprises: Results from the Solar Maximum Mission Bent Crystal Spectrometer

Sylwester

Phillips

et al. 2022

ApJ

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The calcium abundance in flare plasmas is estimated using X-ray spectra from the Solar Maximum Mission Bent Crystal Spectrometer (BCS) during the decays of 194 flares (Geostationary Operational Environmental Satellite, GOES, classifications from B6.4 to X13) occurring between 1980 and 1989. Previous work by Sylwester et al. found that the abundance varied from flare to flare. That analysis is improved on here using updated instrument parameters and by including all calcium lines viewed by the BCS instead of only the resonance line, so greatly enhancing the photon count statistics. The abundance variations are confirmed with the average abundance, A(Ca) (expressed logarithmically with A(H) = 12), equal to 6.77 ± 0.20 for 194 flares (141 of which are new in this study). This range corresponds to factors of between 1.7 and 7.2 larger than the photospheric abundance, and so our results are in line with a “first ionization potential” (FIP) effect whereby low-FIP elements like Ca (FIP = 6.11 eV) have enhanced coronal abundances. The Ca flare abundance is uncorrelated with solar activity indices, but weak correlations are suggested with GOES flare class and duration (larger A(Ca) for smaller and shorter flares). The ponderomotive force theory of Laming explaining the FIP effect gives a range of parameters within which our estimates of A(Ca) agree with the theory. However, this then gives rise to disagreements with previous estimates of the flare silicon and sulfur abundances, although those of argon and iron are in good agreement. Small adjustments of the theory may thus be necessary.

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Section: Introductionmentioning

confidence: 99%

New Solar Flare Calcium Abundances with No Surprises: Results from the Solar Maximum Mission Bent Crystal Spectrometer

Sylwester

Phillips

et al. 2022

ApJ

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“…The remote-sensing observations have been widely used to investigate the MFR formation process [26,31,32]. The charge states within ICMEs are frozen-in near the Sun [33], and the relative abundances of elements with different first ionization potentials (FIPs) are different obviously in the corona and photosphere [34,35]. As the composition does not alter during CME propagation to 1 AU and beyond [36], the in situ data are also employed to analyze the MFR formation [28,37,38] and plasma origin [39,40] of CMEs.…”

Section: Introductionmentioning

confidence: 99%

The Inhomogeneity of Composition Along the Magnetic Cloud Axis

Song

Cheng

et al. 2021

Front. Phys.

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Coronal mass ejections (CMEs) are one of the most energetic explosions in the solar system. It is generally accepted that CMEs result from eruptions of magnetic flux ropes, which are dubbed as magnetic clouds (MCs) in interplanetary space. The composition (including the ionic charge states and elemental abundances) is determined prior to and/or during CME eruptions in the solar atmosphere and does not alter during MC propagation to 1 AU and beyond. It has been known that the composition is not uniform within a cross section perpendicular to the MC axis, and the distribution of ionic charge states within a cross section provides us an important clue to investigate the formation and eruption processes of flux ropes due to the freeze-in effect. The flux rope is a three-dimensional magnetic structure intrinsically, and it remains unclear whether the composition is uniform along the flux rope axis as most MCs are only detected by one spacecraft. In this study, we report an MC that was observed by Advanced Composition Explorer at ∼1 AU during March 4–6, 1998, and Ulysses at ∼5.4 AU during March 24–28, 1998, sequentially. At these times, both spacecraft were located around the ecliptic plane, and the latitudinal and longitudinal separations between them were ∼2.2° and ∼5.5°, respectively. It provides us an excellent opportunity to explore the axial inhomogeneity of flux rope composition, as both spacecraft almost intersected the cloud center at different sites along its axis. Our study shows that the average values of ionic charge states exhibit significant difference along the axis for carbon, and the differences are relatively slight but still obvious for charge states of oxygen and iron as well as the elemental abundances of iron and helium. Besides the means, the composition profiles within the cloud measured by both spacecraft also exhibit some discrepancies. We conclude that the inhomogeneity of composition exists along the cloud axis.

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“…The statistical analysis of these tiny flares demonstrates the possible role of nanoflares in heating the quietest solar corona during this period. The instrument has also been used to study elemental abundances of the 2 MK quiescent solar corona during the aforementioned solar minimum (Vadawale et al 2021b). During this time, the coronal FIP bias was found to be about 2, less than the FIP bias of an active region (around 3-4).…”

Section: Introductionmentioning

confidence: 99%

Evolution of Elemental Abundances During B-Class Solar Flares: Soft X-ray Spectral Measurements with Chandrayaan-2 XSM

Mondal,

Sarkar,

Vadawale

et al. 2021

Preprint

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The Solar X-ray Spectrometer (XSM) payload onboard Chandrayaan-2 provides disk-integrated solar spectra in the 1 -15 keV energy range with an energy resolution of 180 eV (at 5.9 keV) and a cadence of 1 second. During the period from September 2019 to May 2020, covering the minimum of Solar Cycle 24, it observed nine B-class flares ranging from B1.3 to B4.5. Using time-resolved spectroscopic analysis during these flares, we examined the evolution of temperature, emission measure, and absolute elemental abundances of four elements -Mg, Al, Si, and S. These are the first measurements of absolute abundances during such small flares and this study offers a unique insight into the evolution of absolute abundances as the flares evolve. Our results demonstrate that the abundances of these four elements decrease towards their photospheric values during the peak phase of the flares. During the decay phase, the abundances are observed to quickly return to their pre-flare coronal values. The depletion of elemental abundances during the flares is consistent with the standard flare model, suggesting the injection of fresh material into coronal loops as a result of chromospheric evaporation. To explain the quick recovery of the so-called coronal "First Ionization Potential (FIP) bias" we propose two scenarios based on the Ponderomotive force model.

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Observations of the Quiet Sun during the Deepest Solar Minimum of the Past Century with Chandrayaan-2 XSM: Elemental Abundances in the Quiescent Corona

Cited by 21 publications

References 44 publications

New Solar Flare Calcium Abundances with No Surprises: Results from the Solar Maximum Mission Bent Crystal Spectrometer

New Solar Flare Calcium Abundances with No Surprises: Results from the Solar Maximum Mission Bent Crystal Spectrometer

The Inhomogeneity of Composition Along the Magnetic Cloud Axis

Evolution of Elemental Abundances During B-Class Solar Flares: Soft X-ray Spectral Measurements with Chandrayaan-2 XSM

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