Helium Emissions Observed in Ground-Based Spectra of Solar Prominences
Additional information
Authors
Ramelli R.,
Stellmacher G.,
Wiehr E.,
Bianda M.
Type
Journal Article
Year
2012
Language
English
Abstract
The only prominent line of singly ionized helium in the visible spectral range, He II 4686 Å, is observed together with the He I 5015 Å singlet and the He I 4471 Å triplet line in solar prominences. The Na D2 emission is used as a tracer for He II emissions which are sufficiently bright to exceed the noise level near 10−6 of the disk-center intensity. The prominences thus selected are characterized by small non-thermal line broadening and almost absent velocity shifts, yielding narrow line profiles without wiggles. The reduced widths [ΔλD/λ] of He II 4686 Å are 1.5 times broader than those of the He I 4471 Å triplet and 1.65 times broader than those of the He I 5015 Å singlet. This indicates that the He lines originate in a prominence-corona transition region with outwards increasing temperature.
Journal
Solar Physics
Volume
281
Start page number
697
End page number
706
Keywords
irsol-refereed-scientific-papers
