# Suppression of Hydrogen Emission in an X-class White-light Solar Flare

## TL;DR

This study combines observations and simulations to show that in an X-class solar flare, energy is deposited in the lower atmosphere, causing white-light emission without hydrogen line emission.

## Contribution

It provides new insights into energy deposition layers in solar flares, explaining white-light emission without hydrogen line enhancement.

## Key findings

- White-light emission occurs with suppressed hydrogen lines.
- Energy deposition is concentrated in lower atmospheric layers.
- Simulations support a lower atmospheric energy deposition model.

## Abstract

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.