Observations and Modelling of White Light Solar Flares

The bulk of the enhanced radiation emitted during solar flares originates from the lower atmosphere, making it a crucial region for understanding energy, radiation and mass transport during flares. Of the radiation emitted from the lower atmosphere a significant contribution is from enhancements to the optical continuum (white light flares; WLFs). There is still not a consensus regarding the emission mechanisms responsible for WLFs, in part due to the paucity of broadband WLF spectra leading to ambiguity. We present results from modelling the optical continuum during solar flares driven by electron beams, using the RADYN radiation hydrodynamics code. A range of non-thermal electron beam distributions were modelled covering a large part of parameter space. The synthetic continuum originated in the mid-upper chromosphere, and was predominantly the result of optically thin hydrogen recombination radiation. In the simulations in which the beam penetrated deepest there was a non-negligible contribution from enhanced H- opacity, though we were unable to model solely optically thick photospheric sources. Using joint Hinode/SOT and IRIS/SG observations of an X-class flare we assess if the models stand up to scrutiny.