Modelling of Mg II lines in solar prominences. (arXiv:1902.00086v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Levens_P/0/1/0/all/0/1">Peter James Levens</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Labrosse_N/0/1/0/all/0/1">Nicolas Labrosse</a>
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.
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.
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