Non-thermal and Kappa Distributions in Solar Flare Radiative Signatures

Solar flare radiation signatures show evidence of non-thermal distributions pointing to high-energy electron distributions and non-Gaussian plasma turbulence processes. The Kappa function has become an important diagnostic tool in recent years to study these signatures in a quantitative way and connect them to specific physical processes of particle acceleration and transport. In solar flares, the thermal emission of the heated background plasma and the bremsstrahlung from non-thermal electrons are usually superimposed. The Kappa distribution, commonly employed to describe solar wind particle spectra, can also be a useful tool to describe this effect for solar flare electrons with a unified treatment. Here, we discuss the context of solar flare observations and modelling and review the current state of the application of Kappa distributions in solar flare research.