Helium line formation in a solar active region
An observing campaign coordinated between ground based and SOHO instruments has been planned to obtain simultaneous spectroheliograms of the same area in several spectral lines. The chromospheric lines Ca II K, Hα and Na I D, as well as the He I 10830, 5876, 584 and He II 304 Å lines, have been obse...
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2005
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| Acceso en línea: | https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_03796566_v_n560II_p811_Mauas http://hdl.handle.net/20.500.12110/paper_03796566_v_n560II_p811_Mauas |
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paper:paper_03796566_v_n560II_p811_Mauas |
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paper:paper_03796566_v_n560II_p811_Mauas2023-06-08T15:40:42Z Helium line formation in a solar active region Sun: abundances Sun: activity Sun: Helium Infrared radiation Photoionization Photons Plasmas Scanning electron microscopy Solar energy Sun Ultraviolet radiation Spectroheliograms Sun: abundances Sun: activity Sun: Helium Helium An observing campaign coordinated between ground based and SOHO instruments has been planned to obtain simultaneous spectroheliograms of the same area in several spectral lines. The chromospheric lines Ca II K, Hα and Na I D, as well as the He I 10830, 5876, 584 and He II 304 Å lines, have been observed. These observations allow us to build semi-empirical models of the chromosphere and low transition region of an active region, taking into account the photoionizing photons impinging on it. We obtained a model that matches very well all the observed line profiles, using the standard value of the He abundance ([He]=0.1). We studied the influence of the coronal radiation on the computed helium lines and found that, even in an active region, the incident coronal radiation has a limited effect on the UV He lines, while it results of fundamental importance for the D3 and 10830 lines. Finally, we built two more models assuming values of the He abundance [He]=0.07 and 1.5, only in the region where the temperatures are larger than 10000 K and found that the observations can still be well reproduced in both cases. This implies that, to choose between different values of [He], it is necessary to constrain the transition region with different observables, independent of the He lines. 2005 https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_03796566_v_n560II_p811_Mauas http://hdl.handle.net/20.500.12110/paper_03796566_v_n560II_p811_Mauas |
| institution |
Universidad de Buenos Aires |
| institution_str |
I-28 |
| repository_str |
R-134 |
| collection |
Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) |
| topic |
Sun: abundances Sun: activity Sun: Helium Infrared radiation Photoionization Photons Plasmas Scanning electron microscopy Solar energy Sun Ultraviolet radiation Spectroheliograms Sun: abundances Sun: activity Sun: Helium Helium |
| spellingShingle |
Sun: abundances Sun: activity Sun: Helium Infrared radiation Photoionization Photons Plasmas Scanning electron microscopy Solar energy Sun Ultraviolet radiation Spectroheliograms Sun: abundances Sun: activity Sun: Helium Helium Helium line formation in a solar active region |
| topic_facet |
Sun: abundances Sun: activity Sun: Helium Infrared radiation Photoionization Photons Plasmas Scanning electron microscopy Solar energy Sun Ultraviolet radiation Spectroheliograms Sun: abundances Sun: activity Sun: Helium Helium |
| description |
An observing campaign coordinated between ground based and SOHO instruments has been planned to obtain simultaneous spectroheliograms of the same area in several spectral lines. The chromospheric lines Ca II K, Hα and Na I D, as well as the He I 10830, 5876, 584 and He II 304 Å lines, have been observed. These observations allow us to build semi-empirical models of the chromosphere and low transition region of an active region, taking into account the photoionizing photons impinging on it. We obtained a model that matches very well all the observed line profiles, using the standard value of the He abundance ([He]=0.1). We studied the influence of the coronal radiation on the computed helium lines and found that, even in an active region, the incident coronal radiation has a limited effect on the UV He lines, while it results of fundamental importance for the D3 and 10830 lines. Finally, we built two more models assuming values of the He abundance [He]=0.07 and 1.5, only in the region where the temperatures are larger than 10000 K and found that the observations can still be well reproduced in both cases. This implies that, to choose between different values of [He], it is necessary to constrain the transition region with different observables, independent of the He lines. |
| title |
Helium line formation in a solar active region |
| title_short |
Helium line formation in a solar active region |
| title_full |
Helium line formation in a solar active region |
| title_fullStr |
Helium line formation in a solar active region |
| title_full_unstemmed |
Helium line formation in a solar active region |
| title_sort |
helium line formation in a solar active region |
| publishDate |
2005 |
| url |
https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_03796566_v_n560II_p811_Mauas http://hdl.handle.net/20.500.12110/paper_03796566_v_n560II_p811_Mauas |
| _version_ |
1768546255564177408 |