# Modelling of Mg II lines in solar prominences

## TL;DR

This study models Mg II line profiles in solar prominences using non-LTE radiative transfer to understand how physical conditions affect observed spectral shapes, aiding interpretation of prominence observations.

## Contribution

It provides a detailed analysis of how prominence plasma parameters influence Mg II line profiles using comprehensive radiative transfer modeling, enhancing interpretation of solar prominence spectra.

## Key findings

- Most prominences emitting Mg II lines are cold, low-pressure, and optically thick.
- Strong correlations exist between Mg II k line intensities and hydrogen line intensities.
- One-dimensional non-LTE models effectively reproduce main spectral features.

## Abstract

Observations of the Mg II h and k lines in solar prominences with IRIS reveal a wide range of line shapes from simple non-reversed profiles to typical double-peaked reversed profiles with many other complex line shapes possible. The physical conditions responsible for this variety are not well understood. Our aim is to understand how physical conditions inside a prominence slab influence shapes and properties of emergent Mg II line profiles. We compute the spectrum of Mg II lines using a one-dimensional non-LTE radiative transfer code for two large grids of model atmospheres (isothermal isobaric, and with a transition region). The influence of the plasma parameters on the emergent spectrum is discussed in detail. Our results agree with previous studies. We present several dependencies between observables and prominence parameters which will help with interpretation of observations. A comparison with known limits of observed line parameters suggests that most observed prominences emitting in Mg II h and k lines are cold, low pressure, and optically thick structures. Our results indicate that there are good correlations between the Mg II k line intensities and the intensities of hydrogen lines, as well as the emission measure. One-dimensional non-LTE radiative transfer codes are well-suited to understand the main characteristics of the Mg II h and k line profiles in solar prominences, but more advanced codes will be necessary for detailed comparisons.