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Red-shifted components of chromospheric emission lines in the hard X-rayimpulsive phase of solar flares have recently been studied through their 30 sevolution with the high resolution of IRIS. Radiative-hydrodynamic flare modelsshow that these redshifts are generally reproduced by electron-beam generatedchromospheric condensations. The models produce large ambient electrondensities, and the pressure broadening of hydrogen Balmer series should bereadily detected in observations. To accurately interpret upcoming spectraldata of flares with the DKIST, we incorporate non-ideal, non-adiabatic linebroadening profiles of hydrogen into the RADYN code. These improvements allowtime-dependent predictions for the extreme Balmer line wing enhancements insolar flares. We study two chromospheric condensation models, which cover arange of electron beam fluxes ($1-5 \times 10^{11}$ erg s$^{-1}$ cm$^{-2}$) andambient electron densities ($1 - 60 \times 10^{13}$ cm$^{-3}$) in the flarechromosphere. Both models produce broadening and redshift variations within 10s of the onset of beam heating. In the chromospheric condensations, there isenhanced spectral broadening due to large optical depths at H$\alpha$,H$\beta$, and H$\gamma$, while the much lower optical depth of the Balmerseries H12$-$H16 provides a translucent window into the smaller electrondensities in the beam-heated layers below the condensation. The wavelengthranges of typical DKIST/ViSP spectra of solar flares will be sufficient to testthe predictions of extreme hydrogen wing broadening and accurately constrainlarge densities in chromospheric condensations.

astrophysical journal/the astrophysical journal

The Atmospheric Response to High Nonthermal Electron Beam Fluxes in  Solar Flares. II. Hydrogen Broadening Predictions for Solar Flare  Observations with the Daniel K. Inouye Solar Telescope