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The Na i and Sr ii Resonance Lines in Solar Prominences

Abstract : We estimate the electron density, ne, and its spatial variation in quiescent prominences from the observed emission ratio of the resonance lines Na i 5890 Å (D2) and Sr ii 4078 Å. For a bright prominence (τ_{α}≈25) we obtain a mean ne≈2×10^{10} cm^{-3}; for a faint one (τ _{α }≈4) ne≈4×10^{10} cm^{-3} on two consecutive days with moderate internal fluctuation and no systematic variation with height above the solar limb. The thermal and non-thermal contributions to the line broadening, T_{kin} and V_{nth}, required to deduce ne from the emission ratio Na i/Sr ii cannot be unambiguously determined from observed widths of lines from atoms of different mass. The reduced widths, ΔλD0, of Sr ii 4078 Å show an excess over those from Na D2 and Hδ 4101 Å, assuming the same T_{kin} and V_{nth}. We attribute this excess broadening to higher non-thermal broadening induced by interaction of ions with the prominence magnetic field. This is suggested by the finding of higher macro-shifts of Sr ii 4078 Å as compared to those from Na D2.
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https://hal-insu.archives-ouvertes.fr/insu-03747452
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Submitted on : Monday, August 8, 2022 - 11:36:16 AM
Last modification on : Tuesday, August 9, 2022 - 3:45:00 AM

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G. Stellmacher, E. Wiehr. The Na i and Sr ii Resonance Lines in Solar Prominences. SOLAR PHYSICS, 2017, 292, ⟨10.1007/s11207-017-1103-6⟩. ⟨insu-03747452⟩

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