The HeI abundance in Solar filaments
Three filaments observed with the CDS instrument on the SOHO satellite are analysed to determine the HeI/HI ratio. The HI and Hel bound-free absorptions are the major processes responsible for the lower intensity of transition region (TR) lines observed above filaments. One of the filaments was also...
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| Veröffentlicht in: | Astronomy and astrophysics (Berlin) 2005-12, Vol.443 (3), p.1055-1059 |
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| creator | Chiuderi Drago, F. |
| description | Three filaments observed with the CDS instrument on the SOHO satellite are analysed to determine the HeI/HI ratio. The HI and Hel bound-free absorptions are the major processes responsible for the lower intensity of transition region (TR) lines observed above filaments. One of the filaments was also observed by SUMER at $\lambda > 912$ Å, thus supplying the unabsorbed background intensity. The HI and Hel column densities are derived from several TR lines using a least squares method applied to two different models. The resulting HeI/HI ratio is independent of the model, while the column densities are different by about a factor of two. This difference enables us to discriminate between the two models by comparing the resulting value of the optical depth at the Lyman continuum limit, $\tau_{912}$, with previous observations and models. |
| doi_str_mv | 10.1051/0004-6361:20053341 |
| format | Article |
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The HI and Hel bound-free absorptions are the major processes responsible for the lower intensity of transition region (TR) lines observed above filaments. One of the filaments was also observed by SUMER at $\lambda > 912$ Å, thus supplying the unabsorbed background intensity. The HI and Hel column densities are derived from several TR lines using a least squares method applied to two different models. The resulting HeI/HI ratio is independent of the model, while the column densities are different by about a factor of two. 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The HI and Hel bound-free absorptions are the major processes responsible for the lower intensity of transition region (TR) lines observed above filaments. One of the filaments was also observed by SUMER at $\lambda > 912$ Å, thus supplying the unabsorbed background intensity. The HI and Hel column densities are derived from several TR lines using a least squares method applied to two different models. The resulting HeI/HI ratio is independent of the model, while the column densities are different by about a factor of two. This difference enables us to discriminate between the two models by comparing the resulting value of the optical depth at the Lyman continuum limit, $\tau_{912}$, with previous observations and models.</abstract><pub>EDP Sciences</pub><doi>10.1051/0004-6361:20053341</doi><tpages>5</tpages><oa>free_for_read</oa></addata></record> |
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| ispartof | Astronomy and astrophysics (Berlin), 2005-12, Vol.443 (3), p.1055-1059 |
| issn | 0004-6361 1432-0746 |
| language | eng |
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| source | Bacon EDP Sciences France Licence nationale-ISTEX-PS-Journals-PFISTEX; EDP Sciences; Elektronische Zeitschriftenbibliothek - Frei zugängliche E-Journals |
| subjects | Sun: filaments Sun: UV radiation |
| title | The HeI abundance in Solar filaments |
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