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Journal Articles Astronomy and Astrophysics - A&A Year : 2015

Non-thermal line-broadening in solar prominences

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1
E. Wiehr
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Abstract


Aims: We show that the line broadening in quiescent solar prominences is mainly due to non-thermal velocities.
Methods: We have simultaneously observed a wide range of optically thin lines in quiescent prominences, selected for bright and narrow Mg b emission without line satellites from macro-shifts.
Results: We find a ratio of reduced widths, ΔλD0, of Hγ and Hδ of 1.05 ± 0.03, which can hardly be attributed to saturation, since both are optically thin for the prominences observed: τγ ≤ 0.3, τδ ≤ 0.15. We confirm the ratio of reduced widths of He 4772 (triplet) and He 5015 (singlet) of 1.1 ± 0.05 at higher significance and detect a width ratio of Mg b2 and Mg 4571 (both from the triplet system) of 1.3 ± 0.1.
Conclusions: The discrepant widths of lines from different atoms, and even from the same atom, cannot be represented by a unique pair [Tkin; Vnth]. Values of Tkin deduced from observed line radiances using models indicate low temperatures down to Tkin ≈ 5000 K. Non-thermal velocities, related to different physical states of the respective emitting prominence region, seem to be the most important line broadening mechanism.
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Dates and versions

insu-03644874 , version 1 (28-04-2022)

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G. Stellmacher, E. Wiehr. Non-thermal line-broadening in solar prominences. Astronomy and Astrophysics - A&A, 2015, 581, ⟨10.1051/0004-6361/201322781⟩. ⟨insu-03644874⟩
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