Spectral Features of the Solar Transition Region and Chromospheric Lines at Flare Ribbons Observed with IRIS
We report on the spectral features of the Si iv λ 1402.77, C ii λ 1334.53, and Mg ii h or k lines, formed in the layers from the transition region to the chromosphere, in three two-ribbon flares (with X, M, and C class) observed with IRIS. All three lines show significant redshifts within the main f...
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| Format: | Artykuł |
| Język: | English |
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IOP Publishing
2023-01-01
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| Seria: | The Astrophysical Journal Supplement Series |
| Hasła przedmiotowe: | |
| Dostęp online: | https://doi.org/10.3847/1538-4365/acf127 |
| _version_ | 1827798858688626688 |
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| author | L. F. Wang Y. Li Q. Li X. Cheng M. D. Ding |
| author_facet | L. F. Wang Y. Li Q. Li X. Cheng M. D. Ding |
| author_sort | L. F. Wang |
| collection | DOAJ |
| description | We report on the spectral features of the Si iv λ 1402.77, C ii λ 1334.53, and Mg ii h or k lines, formed in the layers from the transition region to the chromosphere, in three two-ribbon flares (with X, M, and C class) observed with IRIS. All three lines show significant redshifts within the main flare ribbons, which mainly originate from the chromospheric condensation during the flares. The average redshift velocities of the Si iv line within the main ribbons are 56.6, 25.6, and 10.5 km s ^−1 for the X-, M-, and C-class flares, respectively, which show a decreasing tendency with the flare class. The C ii and Mg ii lines show a similar tendency but with smaller velocities compared to the Si iv line. Additionally, the Mg ii h or k line shows a blue-wing enhancement in the three flares, in particular at the flare ribbon fronts, which is supposed to be caused by an upflow in the upper chromosphere due to the heating of the atmosphere. Moreover, the Mg ii h or k line exhibits a central reversal at the flare ribbons but turns to pure emission shortly after 1–4 minutes. Correspondingly, the C ii line also shows a central reversal but in a smaller region. However, for the Si iv line, the central reversal is only found in the X-class flare. As usual, the central reversal of these lines can be caused by the opacity effect. This implies that, in addition to the optically thick lines (C ii and Mg ii lines), the Si iv line can become optically thick in a strong flare, which is likely related to the nonthermal electron beam heating. |
| first_indexed | 2024-03-11T19:42:02Z |
| format | Article |
| id | doaj.art-f176110e5cc74b80a1b26b51192c5e43 |
| institution | Directory Open Access Journal |
| issn | 0067-0049 |
| language | English |
| last_indexed | 2024-03-11T19:42:02Z |
| publishDate | 2023-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astrophysical Journal Supplement Series |
| spelling | doaj.art-f176110e5cc74b80a1b26b51192c5e432023-10-06T08:40:35ZengIOP PublishingThe Astrophysical Journal Supplement Series0067-00492023-01-0126826210.3847/1538-4365/acf127Spectral Features of the Solar Transition Region and Chromospheric Lines at Flare Ribbons Observed with IRISL. F. Wang0https://orcid.org/0000-0002-0156-5180Y. Li1https://orcid.org/0000-0002-8258-4892Q. Li2https://orcid.org/0000-0001-7540-9335X. Cheng3https://orcid.org/0000-0003-2837-7136M. D. Ding4https://orcid.org/0000-0002-4978-4972School of Astronomy and Space Science, Nanjing University , Nanjing 210023, People's Republic of China ; dmd@nju.edu.cn; Key Laboratory of Modern Astronomy and Astrophysics (Nanjing University) , Ministry of Education, Nanjing 210023, People's Republic of ChinaKey Laboratory of Dark Matter and Space Astronomy, Purple Mountain Observatory , Chinese Academy of Sciences, Nanjing 210023, People's Republic of China ; yingli@pmo.ac.cn; School of Astronomy and Space Science, University of Science and Technology of China , Hefei 230026, People’s Republic of ChinaKey Laboratory of Dark Matter and Space Astronomy, Purple Mountain Observatory , Chinese Academy of Sciences, Nanjing 210023, People's Republic of China ; yingli@pmo.ac.cn; School of Astronomy and Space Science, University of Science and Technology of China , Hefei 230026, People’s Republic of ChinaSchool of Astronomy and Space Science, Nanjing University , Nanjing 210023, People's Republic of China ; dmd@nju.edu.cn; Key Laboratory of Modern Astronomy and Astrophysics (Nanjing University) , Ministry of Education, Nanjing 210023, People's Republic of ChinaSchool of Astronomy and Space Science, Nanjing University , Nanjing 210023, People's Republic of China ; dmd@nju.edu.cn; Key Laboratory of Modern Astronomy and Astrophysics (Nanjing University) , Ministry of Education, Nanjing 210023, People's Republic of ChinaWe report on the spectral features of the Si iv λ 1402.77, C ii λ 1334.53, and Mg ii h or k lines, formed in the layers from the transition region to the chromosphere, in three two-ribbon flares (with X, M, and C class) observed with IRIS. All three lines show significant redshifts within the main flare ribbons, which mainly originate from the chromospheric condensation during the flares. The average redshift velocities of the Si iv line within the main ribbons are 56.6, 25.6, and 10.5 km s ^−1 for the X-, M-, and C-class flares, respectively, which show a decreasing tendency with the flare class. The C ii and Mg ii lines show a similar tendency but with smaller velocities compared to the Si iv line. Additionally, the Mg ii h or k line shows a blue-wing enhancement in the three flares, in particular at the flare ribbon fronts, which is supposed to be caused by an upflow in the upper chromosphere due to the heating of the atmosphere. Moreover, the Mg ii h or k line exhibits a central reversal at the flare ribbons but turns to pure emission shortly after 1–4 minutes. Correspondingly, the C ii line also shows a central reversal but in a smaller region. However, for the Si iv line, the central reversal is only found in the X-class flare. As usual, the central reversal of these lines can be caused by the opacity effect. This implies that, in addition to the optically thick lines (C ii and Mg ii lines), the Si iv line can become optically thick in a strong flare, which is likely related to the nonthermal electron beam heating.https://doi.org/10.3847/1538-4365/acf127Solar activitySolar flaresSolar transition regionSolar chromosphereSolar ultraviolet emissionSolar flare spectra |
| spellingShingle | L. F. Wang Y. Li Q. Li X. Cheng M. D. Ding Spectral Features of the Solar Transition Region and Chromospheric Lines at Flare Ribbons Observed with IRIS The Astrophysical Journal Supplement Series Solar activity Solar flares Solar transition region Solar chromosphere Solar ultraviolet emission Solar flare spectra |
| title | Spectral Features of the Solar Transition Region and Chromospheric Lines at Flare Ribbons Observed with IRIS |
| title_full | Spectral Features of the Solar Transition Region and Chromospheric Lines at Flare Ribbons Observed with IRIS |
| title_fullStr | Spectral Features of the Solar Transition Region and Chromospheric Lines at Flare Ribbons Observed with IRIS |
| title_full_unstemmed | Spectral Features of the Solar Transition Region and Chromospheric Lines at Flare Ribbons Observed with IRIS |
| title_short | Spectral Features of the Solar Transition Region and Chromospheric Lines at Flare Ribbons Observed with IRIS |
| title_sort | spectral features of the solar transition region and chromospheric lines at flare ribbons observed with iris |
| topic | Solar activity Solar flares Solar transition region Solar chromosphere Solar ultraviolet emission Solar flare spectra |
| url | https://doi.org/10.3847/1538-4365/acf127 |
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