Non-LTE inversion of prominence spectroscopic observations in Hα and Mg II h&k lines

Jejčič, Sonja (author), Heinzel, Petr (author), Schmieder, Brigitte (author), Gunár, Stanislav (author), Mein, Pierre (author), Mein, Nicole (author), Ruan, Guiping (author)

We continued our investigation of the plasma characteristics of a quiescent prominence that occurred on 2017 March 30. The prominence was observed simultaneously by several instruments, including the Interface Region Imaging Spectrograph (IRIS) and the Multichannel Subtractive Double Pass (MSDP) spectrograph operating at the Meudon solar tower. We focused on IRIS Mg II h&k and MSDP Hα spectra, selecting 55 well-coaligned points within the prominence. We computed an extensive grid of 63,000 isothermal and isobaric 1D-slab prominence models with a non-LTE (i.e., departures from the local thermodynamic equilibrium) radiative transfer code. We then performed a 1.5D spectral inversion searching for an optimal model that best fits five parameters of the observed profiles (observables), namely, the integrated intensity of the Hα and Mg II k lines, the FWHM of both lines, and the ratio of intensities of the Mg II k and Mg II h lines. The latter is sensitive to temperature. Our results show that the prominence is a low-temperature structure, mostly below 10,000 K, with some excursions to higher values (up to 18,000 K) but also rather low temperatures (around 5000 K). The microturbulent velocity is typically low, peaking around 8 km s$^{−1}$, and electron density values are of the order of 10$^{10}$ cm$^{−3}$. The peak effective thickness is 500 km, although the values range up to 5000 km. The studied prominence is rather optically thin in the Hα line and optically thick in the Mg II h&k lines.

• Language: English
• Keywords: solar prominences, radiative transfer, spectroscopy, quiescent solar prominence
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: PEF - Faculty of Education; FMF - Faculty of Mathematics and Physics
• Publication status: Published
• Publication version: Version of Record
• Year: 2022
• Number of pages: 12 str.
• Numbering: Vol. 932, no. 1, art. 3
• PID: 20.500.12556/RUL-145192
• UDC: 523.9
• ISSN on article: 1538-4357
• DOI: 10.3847/1538-4357/ac6bf5
• COBISS.SI-ID: 115353091
• Publication date in RUL: 13.04.2023

Record is a part of a journal

• Title: The Astrophysical journal
• Shortened title: Astrophys. j.
• Publisher: University of Chicago Press for the American Astronomical Society
• ISSN: 1538-4357
• COBISS.SI-ID: 515079705

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.

Secondary language

• Language: Slovenian
• Keywords: sončeve protuberance, sevalni prenos, spektroskopija