Simulation of the April 27, 2012 Flare Emission in the Spectral Lines of Hydrogen, Helium, and Calcium

The paper presents the results of the analysis of the sloar flare SOL2012-04-27 emission in hydrogen, helium, and calcium spectral lines observed on the horizontal solar facility HSFA-2 of the Ondřejov Observatory (Astronomical Institute of the Czech Academy of Sciences). After processing the spectra, the integrated emission fluxes in the lines were determined. The data collected are treated using the approach of rapid energy release inside the chromosphere, accompanied by gas evaporation. Within the framework of the heated gas model, a theoretical calculation of the plasma parameters was performed, taking into account the physical conditions in the chromosphere, including spectral line self-absorption. Comparison across six lines allowed, with a high degree of validity, the reconstruction of the temperature \(T\) , density, and spatial structure of the emitting gas. The best agreement of theory with observations is obtained in the model of the spread of inhomogeneous clouds, each of which has hot ( \(T\approx 18\,000{-}19\,500\) K) and less heated ( \(T\approx 8000{-}9000\) K) regions. On average, one cloud contributes about ten percent to the total emission flux.