Cole Tamburri, Adam Kowalski, Gianna Cauzzi, Maria Kazachenko, Alexandra Tritschler, Rahul Yadav, Ryan French, Yuta Notsu, Kevin Reardon, Isaiah Tristan

We analyze decay phase observations of the GOES class C6.7 flare SOL2022-08-19T20:31 by the Visible Spectropolarimeter (ViSP) on the National Science Foundation's Daniel K. Inouye Solar Telescope (DKIST). The data include the first flare-time DKIST observations of the chromospheric Ca II H 396.8 nm and H-epsilon 397.0 nm spectral lines. These diagnostics have rarely been studied together during the modern era of high-resolution solar flare observations, and never at the spectral and spatial resolution of the DKIST. We directly compare DKIST spectra to state-of-the-art RADYN+RH simulations, including one heated by a nonthermal electron beam and one by in-situ thermal conduction. While certain salient properties of the spectra such as the width of H-epsilon are reproduced, the models severely underestimate the width of Ca II H in the red wing and fail to reproduce the exact relative intensity of Ca II H to H-epsilon. The models exhibit a range of condensation electron densities spanning over an order of magnitude. Unlike the modeled lower-order Balmer-series lines, we find that the width of H-epsilon is not solely related to the condensation properties; the widths and intensities are also sensitive to the deeper flare layers. We outline possible avenues towards improvement of flare models, such as a comprehensive evaluation of flare heating mechanisms in the context of both impulsive and decay phase high-resolution data.