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High-density Off-limb Flare Loops Observed by SDO
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SYSNO ASEP 0497539 Document Type J - Journal Article R&D Document Type Journal Article Subsidiary J Článek ve WOS Title High-density Off-limb Flare Loops Observed by SDO Author(s) Jejčič, Sonja (ASU-R)
Kleint, L. (CH)
Heinzel, Petr (ASU-R) RID, ORCIDArticle number 134 Source Title Astrophysical Journal - ISSN 0004-637X
Roč. 867, č. 2 (2018)Number of pages 10 s. Publication form Online - E Language eng - English Country US - United States Keywords Sun ; flares ; radio radiation Subject RIV BN - Astronomy, Celestial Mechanics, Astrophysics OECD category Astronomy (including astrophysics,space science) R&D Projects GA16-18495S GA ČR - Czech Science Foundation (CSF) GA16-16861S GA ČR - Czech Science Foundation (CSF) Method of publishing Open access Institutional support ASU-R - RVO:67985815 UT WOS 000450221700001 EID SCOPUS 85056699532 DOI 10.3847/1538-4357/aae650 Annotation On 2017 September 10, a prominent loop system appeared during the gradual phase of an X8.2 flare (SOL2017-09-10), visible in all passbands of SDO/AIA and in the white-light continuum of SDO/HMI. We investigate its electron density by taking into account all radiation processes in the flare loops, i.e., the Thomson continuum, hydrogen Paschen and Brackett recombination continua, as well as free–free continuum emission. We derive a quadratic function of the electron density for a given temperature and effective loop thickness. By absolutely calibrating SDO/HMI intensities, we convert the measured intensities into electron density at each pixel in the loops. For a grid of plausible temperatures between cool (6000 K) and hot (106 K) structures, the electron density is computed for representative effective thicknesses between 200 and 20,000 km. We obtain a relatively high maximum electron density, about 1013 cm‑3. At such high electron densities, the Thomson continuum is negligible and therefore one would not expect a significant polarization degree in dense loops. We conclude that the Paschen and Brackett recombination continua are dominant in cool flare loops, while the free–free continuum emission is dominant for warmer and hot loops. Workplace Astronomical Institute Contact Radka Svašková, bibl@asu.cas.cz, Tel.: 323 620 326 Year of Publishing 2019 Electronic address http://hdl.handle.net/11104/0290095
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