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  A Si iv/O iv Electron Density Diagnostic for the Analysis of IRIS Solar Spectra

Young, P. R., Keenan, F. P., Milligan, R. O., & Peter, H. (2018). A Si iv/O iv Electron Density Diagnostic for the Analysis of IRIS Solar Spectra. The Astrophysical Journal, 857(1): 5. doi:10.3847/1538-4357/aab556.

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Item Permalink: http://hdl.handle.net/21.11116/0000-0003-4FEF-9 Version Permalink: http://hdl.handle.net/21.11116/0000-0003-4FF0-6
Genre: Journal Article

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Young, P. R., Author
Keenan, F. P., Author
Milligan, R. O., Author
Peter, Hardi1, Author              
Affiliations:
1Department Sun and Heliosphere, Max Planck Institute for Solar System Research, Max Planck Society, ou_1832289              

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 Abstract: Solar spectra of ultraviolet bursts and flare ribbons from the Interface Region Imaging Spectrograph (IRIS) have suggested high electron densities of > 10(12) cm(-3) at transition region temperatures of 0.1 MK, based on large intensity ratios of Si IV lambda 1402.77 to 0 IV lambda 1401.16. In this work, a rare observation of the weak 0 IV lambda 1343.51 line is reported from an X-class flare that peaked at 21:41 UT on 2014 October 24. This line is used to develop a theoretical prediction of the Si IV lambda 1402.77 to 0 IV lambda 1401.16 ratio as a function of density that is recommended to be used in the high-density regime. The method makes use of new pressure-dependent ionization fractions that take account of the suppression of dielectronic recombination at high densities. It is applied to two sequences of flare kernel observations from the October 24 flare. The first shows densities that vary between 3 x 10(12) and 3 x 10(13) cm(-3) over a seven-minute period, while the second location shows stable density values of around 2 x 10(12) cm(-3) over a three-minute period.

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Language(s): eng - English
 Dates: 2019-04-052018
 Publication Status: Published online
 Pages: -
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Identifiers: DOI: 10.3847/1538-4357/aab556
 Degree: -

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Title: The Astrophysical Journal
Source Genre: Journal
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Publ. Info: Bristol; Vienna : IOP Publishing; IAEA
Pages: - Volume / Issue: 857 (1) Sequence Number: 5 Start / End Page: - Identifier: ISSN: 0004-637X
CoNE: https://pure.mpg.de/cone/journals/resource/954922828215_3