Spectroscopic Analysis and RHD Modeling of the First Ca II H and H ϵ Flare Spectra from DKIST/ViSP

Area of Science:

• Solar Physics
• Stellar Astrophysics
• Plasma Physics

Background:

• Solar flares release significant energy and particles.
• Chromospheric diagnostics are crucial for understanding flare dynamics.
• High-resolution observations are essential for validating solar flare models.

Purpose of the Study:

• Analyze decay phase observations of a C6.7 solar flare.
• Compare Visible Spectropolarimeter (ViSP) data from DKIST with RADYN+RH simulations.
• Investigate the spectral line profiles of Ca II H and H epsilon.

Main Methods:

• Utilized Visible Spectropolarimeter (ViSP) on the Daniel K. Inouye Solar Telescope (DKIST).
• Observed decay phase of the GOES C6.7 flare SOL2022-08-19T20:31.
• Compared observational data with RADYN+RH flare simulations (nonthermal electron beam and thermal conduction heating).

Main Results:

• DKIST provided first flare-time observations of Ca II H and H epsilon spectral lines.
• Simulations reproduced H epsilon width but underestimated Ca II H red wing width.
• Models failed to match the relative intensity of Ca II H to H epsilon.
• Chromospheric electron densities in models varied over an order of magnitude.

Conclusions:

• Current flare models need refinement, particularly regarding Ca II H line formation.
• H epsilon line width is sensitive to deeper flare layers, not just the upper chromosphere.
• Further investigation into flare heating mechanisms using high-resolution data is required.