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Can Subphotospheric Magnetic Reconnection Change the Elemental Composition in the Solar Corona?

Baker, D; van Driel-Gesztelyi, L; Brooks, DH; Demoulin, P; Valori, G; Long, DM; Laming, JM; ... James, AW; + view all (2020) Can Subphotospheric Magnetic Reconnection Change the Elemental Composition in the Solar Corona? Astrophysical Journal , 894 (1) , Article 35. 10.3847/1538-4357/ab7dcb. Green open access

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Abstract

Within the coronae of stars, abundances of those elements with low first ionization potential (FIP) often differ from their photospheric values. The coronae of the Sun and solar-type stars mostly show enhancements of low-FIP elements (the FIP effect) while more active stars such as M dwarfs have coronae generally characterized by the inverse-FIP effect (I-FIP). Here we observe patches of I-FIP effect solar plasma in AR 12673, a highly complex βγδ active region. We argue that the umbrae of coalescing sunspots, and more specifically strong light bridges within the umbrae, are preferential locations for observing I-FIP effect plasma. Furthermore, the magnetic complexity of the active region and major episodes of fast flux emergence also lead to repetitive and intense flares. The induced evaporation of the chromospheric plasma in flare ribbons crossing umbrae enables the observation of four localized patches of I-FIP effect plasma in the corona of AR 12673. These observations can be interpreted in the context of the ponderomotive force fractionation model which predicts that plasma with I-FIP effect composition is created by the refraction of waves coming from below the chromosphere. We propose that the waves generating the I-FIP effect plasma in solar active regions are generated by subphotospheric reconnection of coalescing flux systems. Although we only glimpse signatures of I-FIP effect fractionation produced by this interaction in patches on the Sun, on highly active M stars it may be the dominant process.

Type: Article
Title: Can Subphotospheric Magnetic Reconnection Change the Elemental Composition in the Solar Corona?
Open access status: An open access version is available from UCL Discovery
DOI: 10.3847/1538-4357/ab7dcb
Publisher version: http://doi.org/10.3847/1538-4357/ab7dcb
Language: English
Additional information: This version is the version of record. For information on re-use, please refer to the publisher’s terms and conditions.
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Space and Climate Physics
URI: https://discovery.ucl.ac.uk/id/eprint/10093341
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