The Atmospheric Response to Large Electron Beam Fluxes in Solar Flares. III. Comprehensive Modeling of the Brightest Observed Near-ultraviolet Continuum Source in an X9 Solar Flare Journal Article uri icon

Overview

abstract

  • Abstract; ; I report on the high-resolution spectra of the remarkable X9 solar flare of 2024 October 3 (SOL2024-10-03T12:08) and evaluate the extent to which nonthermal electron beams that generate dense chromospheric condensations can power very bright kernels in solar flares. One-dimensional radiative-hydrodynamic models predict extreme H; α; near-wing broadening, bright continuum intensities, and a rapid Fe; II; red wing asymmetry evolution at the brightest near-UV (NUV) continuum source in the flare. Detailed comparisons to the spectral observations reveal that the H; α; line is too broad, the Fe; II; red wing is too bright, and the NUV continuum decays too slowly in a fiducial high-flux beam model. However, chromospheric condensations with maximum electron densities of; n; ; e; ;  ≈ 5 × 10; 14; cm; −3; and optical depths; τ;  ≈ 1 in the near wing of H; α; are consistent with the observed intensity of a broad spectrum in the southern ribbon. Model similarities demonstrate that Fe; i; emission lines and the far-UV (FUV) continuum intensity can form at chromospheric heights during flares, but I find that the ratios of the NUV to FUV continuum intensities are generally too large in the models. This suggests that radiative-hydrodynamic models of chromospheric condensations cool through; T;  ≈ 30,000 K too rapidly. The larger-than-expected FUV continuum intensities are not nearly bright enough to explain recent stellar megaflare spectra from the Hubble Space Telescope.;

publication date

  • January 10, 2026

Date in CU Experts

  • January 28, 2026 10:49 AM

Full Author List

  • Kowalski AF

author count

  • 1

Other Profiles

International Standard Serial Number (ISSN)

  • 0004-637X

Electronic International Standard Serial Number (EISSN)

  • 1538-4357

Additional Document Info

start page

  • 114

end page

  • 114

volume

  • 996

issue

  • 2