PREDNASAJUCI / LECTURER :

Aaron W. Peat

(1) Centre of Scientific Excellence – Solar and Stellar Activity, University of Wrocław, Poland

NAZOV / TITLE :

Working Towards Multispecies Prominence Inversions

ABSTRAKT / ABSTRACT :

It is well known within the prominence community that single species prominence inversions can
lead to degenerate solutions. Additionally, depending on the typical optical depth of the line
in question, only part of the prominence plasma is actually sampled. We work towards constraining
this problem using multispecies observations of a solar prominence with the Swedish Solar Telescope
(SST) and the use of the 1D NLTE (i.e. departures from local thermodynamic equilibrium (LTE))
radiative transfer (RT) code, Promweaver, built on the NLTE RT framework, Lightweaver. These
observations comprise the lines Hα, Hβ, HeI D3, Ca 8542Å, and CaII H.
The profiles are inverted using the Levenberg-Marquardt (LM) gradient descent method for least
squares minimisation, where the residuals of the current model and data are minimised. The starting
guess given to the LM algorithm is found by a basic grid search.
As the initial level populations in Lightweaver are in LTE, the level populations of the previous
guess of the model atmosphere are used as the initial state of the next guess. This helps to speed
up convergence, as prominences are not in LTE. Additionally, for now we use isothermal/isobaric
models to keep the parameter space small. We will summarise the SST observations and showcase our
steps towards attempting to recover the thermodynamic properties of this prominence.