Solar prominences with Na and Mg emissions and centrally reversed Balmer line

TL;DR

This study analyzes bright solar prominences, revealing that sodium and magnesium emissions are linked with centrally reversed hydrogen lines, modeled effectively by semi-infinite atmospheres, and provides insights into temperature and broadening mechanisms.

Contribution

It demonstrates the correlation between Na and Mg emissions and reversed hydrogen line profiles in prominences, with detailed modeling of physical conditions.

Findings

Centrally reversed H-alpha and H-beta profiles are common in prominences with Na and Mg emissions.

Maximum H-alpha source function corresponds to an excitation temperature of about 3950-4000 K.

Non-thermal broadening of 5 km/s is inferred from narrow NaD2 and Mgb2 profiles.

Abstract

We study spectral lines in exceptionally bright solar limb prominences with pronounced sodium and magnesium emission. We find that most prominences with significant NaD2 and Mgb2 emission show centrally reversed profiles of H-alpha and occasionally even of H-beta, which are are well reproduced by semi-infinite models. The maximum H-alpha source function corresponds to an excitation temperature of 3950 K, for pronounced central reversions 4000 K; the related optical thickness exceeds 10.0. The narrow widths of the NaD2 and Mgb2 profiles yield a non-thermal broadening of 5 km/s.