Theoretical Reconstruction of the Parameters of Gas Emitting in the Spectral Lines of the Optical Range of Hydrogen, Helium, and Calcium during the SOL2015-10-01 Flare

Abstract

The solar flare SOL2015-10-01 was observed at the Astronomical Institute of the Czech Academy of Sciences using the HSFA-2 horizontal solar research setup. After processing the spectra, the integral radiation fluxes were determined for the H\(\alpha\), H\(\beta\), and H\(\varepsilon\) lines of hydrogen, the D3 line of helium, as well as the resonance \(\lambda=3968\) Å and infrared \(\lambda=8542\) Ålines of the CaII ion. The analyzed flare exhibited two characteristic cores, and during processing, the fluxes from each core were determined. Within the framework of the heated gas model, theoretical calculations of plasma parameters were performed, taking into account the physical conditions in the chromosphere, including self-absorption in the spectral lines. The simultaneous analysis of six lines from three atomic systems made it possible to reconstruct the temperature, density, and spatial structure of the emitting gas with high confidence. A strong temperature inhomogeneity in the emitting gas was revealed. The reconstructed theoretical gas concentration values exceed those for prominences by at least an order of magnitude, suggesting the chromospheric nature of the emitting gas.