The Ly α and Ly β Profiles in Solar Prominences and Prominence Fine Structure |
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| Authors: | J-C Vial H Ebadi A Ajabshirizadeh |
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| Institution: | (1) Institut d’Astrophysique Spatiale, Unité Mixte, CNRS – Université de Paris XI, Bat 121, 91405 Orsay, France;(2) Faculty of Physics, Tabriz University, Tabriz, Iran;(3) Research Institute for Astronomy and Astrophysics of Maragha, 55134-441 Maragha, Iran |
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| Abstract: | Ly α and Ly β line profiles in a solar prominence were observed with high spatial and spectral resolution with SOHO/SUMER.
Within a 60-arcsec scan, we measure a very large variety of profiles: not only reversed and nonreversed profiles but also
red-peaked and blue-peaked ones in both lines. Such a spatial variability is probably related to both the fine structure in
prominences and the different orientations of mass motions. The usage of integrated-intensity cuts along the SUMER slit allowed
us to categorize the prominence in three regions. We computed average profiles and integrated intensities in these lines in
the range 2.36 – 42.3 W m−2 sr−1 for Ly α and 0.027 – 0.237 W m−2 sr−1 for Ly β. As shown by theoretical modeling, the Ly α/Ly β ratio is very sensitive to geometrical and thermodynamic properties
of fine structure in prominences. For some pixels, and in both lines, we found agreement between observed intensities and
those predicted by one-dimensional models. But a close examination of the profiles indicated a rather systematic disagreement
concerning their detailed shapes. The disagreement between observations and thread models (with ambipolar diffusion) leads
us to speculate about the importance of the temperature gradient between the cool and coronal regions. This gradient could
depend on the orientation of field lines as proposed by Heinzel, Anzer, and Gunár (Astron. Astrophys.
442, 331, 2005). |
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| Keywords: | Sun Prominences Fine structure Ly α and Ly β lines |
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