We present unique NUV observations of a well-observed X-class flare from NOAA 12087 obtained at Ond\v{r}ejov Observatory. The flare shows a strong white-light continuum but no detectable emission in the higher Balmer and Lyman lines. RHESSI and Fermi observations indicate an extremely hard X-ray spectrum and gamma-ray emission. We use the RADYN radiative hydrodynamic code to perform two type of simulations. One where an energy of 3 x 10^11 erg/cm^2/s is deposited by an electron beam with a spectral index of ~3 and a second where the same energy is applied directly to the photosphere. The combination of observations and simulations allow us to conclude that the white-light emission and the suppression or complete lack of hydrogen emission lines is best explained by a model where the dominant energy deposition layer is located in the lower layers of the solar atmosphere rather than the chromosphere.
@article{arxiv.1702.00638,
title = {Suppression of Hydrogen Emission in an X-class White-light Solar Flare},
author = {Ondřej Procházka and Ryan O. Milligan and Joel C. Allred and Adam F. Kowalski and Pavel Kotrč and Mihalis Mathioudakis},
journal= {arXiv preprint arXiv:1702.00638},
year = {2017}
}