Inversion codes allow reconstructing a model atmosphere from observations. With the inclusion of optically thick lines that form in the solar chromosphere, such modelling is computationally very expensive because a non-LTE evaluation of the radiation field is required. In this study, we combine the results provided by these traditional methods with machine and deep learning techniques to obtain similar-quality results in an easy-touse, much faster way. We have applied these new methods to Mg II h&k lines observed by IRIS. As a result, we are able to reconstruct the thermodynamic state (temperature, line-of-sight velocity, non-thermal velocities, electron density, etc.) in the chromosphere and upper photosphere of an area equivalent to an active region in a few CPU minutes, speeding up the process by a factor of 105-106. The open-source code accompanying this paper will allow the community to use IRIS observations to open a new window to a host of solar phenomena.
@article{arxiv.1904.08390,
title = {Recovering Thermodynamics from Spectral Profiles observed by IRIS: A Machine and Deep Learning Approach},
author = {Alberto Sainz Dalda and Jaime de la Cruz Rodríguez and Bart De Pontieu and Milan Gošić},
journal= {arXiv preprint arXiv:1904.08390},
year = {2019}
}