Spectral Characteristics of the Hei D3 Line in a Quiescent Prominence Observed by THEMIS

• Published in: Solar physics 2017-08, Vol.292 (8), p.1
• Main Authors: Koza, Július, Rybák, Ján, Gömöry, Peter, Kozák, Matús, López Ariste, Arturo
• Format: Article
• Language: English
• Subjects: Adequacy; Fluid flow; Normal distribution; Optical thickness; Prominences; Solar physics; Solar system; Spectrum analysis
• ISSN: 0038-0938; 1573-093X
• DOI: 10.1007/s11207-017-1118-z

(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image) We analyze the observations of a quiescent prominence acquired by the Téléscope Heliographique pour l'Étude du Magnetisme et des Instabilités Solaires (THEMIS) in the Hei 5876 Å (Hei D3) multiplet aiming to measure the spectral characteristics of the Hei D3 profiles and to find for them an adequate fitting model. The component characteristics of the Hei D3 Stokes I profiles are measured by the fitting system by approximating them with a double Gaussian. This model yields an Hei D3 component peak intensity ratio of ..., which differs from the value of 8 expected in the optically thin limit. Most of the measured Doppler velocities lie in the interval ±5 kms-1, with a standard deviation of ±1.7 kms-1 around the peak value of 0.4 kms-1. The wide distribution of the full-width at half maximum has two maxima at 0.25 Å and 0.30 Å for the Hei D3 blue component and two maxima at 0.22 Å and 0.31 Å for the red component. The width ratio of the components is ... We show that the double-Gaussian model systematically underestimates the blue wing intensities. To solve this problem, we invoke a two-temperature multi-Gaussian model, consisting of two double-Gaussians, which provides a better representation of Hei D3 that is free of the wing intensity deficit. This model suggests temperatures of 11.5 kK and 91 kK, respectively, for the cool and the hot component of the target prominence. The cool and hot components of a typical Hei D3 profile have component peak intensity ratios of 6.6 and 8, implying a prominence geometrical width of 17 Mm and an optical thickness of 0.3 for the cool component, while the optical thickness of the hot component is negligible. These prominence parameters seem to be realistic, suggesting the physical adequacy of the multi-Gaussian model with important implications for interpreting Hei D3 spectropolarimetry by current inversion codes.