Dependence of the He/H8 emission ratio on brightness, temperature, and structuring of prominences

TL;DR

This study examines how the ratio of helium to hydrogen emission lines in solar prominences varies with brightness and temperature, revealing an anti-correlation influenced by prominence structure and thermal conditions.

Contribution

It provides new observational insights into the dependence of emission line ratios on prominence temperature and brightness, highlighting the role of fine-structure in these phenomena.

Findings

He/H8 emission ratio inversely correlates with H8 brightness.

Higher brightness prominences tend to have lower kinetic temperatures.

Prominences with less fine-structure show more pronounced ratio variations.

Abstract

We investigate the dependence of the He/H8 emission ratio on kinetic temperature and total Balmer brightness. The line pair He\,{\sc i}\,3888\,\AA{} and H$_8$\,3889 has been observed simultaneously with the Ca II 8498 line in a number of quiescent prominences. The He/H8 emission ratio R is found to cover defined parts of a general anti-relation with the total H8 emission, depending on the kinetic temperature, T_kin, of the individual prominence: High H8 brightness is related to small R and T_kin values, and preferably occurs in prominences with a less significant fine-structure.