Spectroscopic Analysis and RHD Modeling of the First Ca II H and H$epsilon $ Flare Spectra from DKIST/ViSP Journal Article uri icon

Overview

abstract

  • Abstract; ; 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 $; ; ϵ; ; ; ; 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 $; ; ϵ; ; ; ; 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 $; ; ϵ; ; ; ; . The models exhibit a range of chromospheric electron densities spanning over an order of magnitude. Unlike the modeled lower-order Balmer-series lines, we find that the width of H; ; ; $epsilon $; ; ϵ; ; ; ; is not solely related to the high-density upper chromosphere; 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.;

publication date

  • March 1, 2026

Date in CU Experts

  • March 5, 2026 12:39 PM

Full Author List

  • Tamburri C; Kowalski A; Cauzzi G; Kazachenko M; Tritschler A; Yadav R; French R; Notsu Y; Reardon K; Tristan I

author count

  • 10

Other Profiles

International Standard Serial Number (ISSN)

  • 0038-0938

Electronic International Standard Serial Number (EISSN)

  • 1573-093X

Additional Document Info

volume

  • 301

issue

  • 3

number

  • 38