can easily be observed in chromospheric spectral lines, such as H$\alpha$. It is believed that the chromospheric-line emission is stimulated by the collisional excitation of the chromosphere under the reconnection site by electron beams that are accelerated during the reconnection.

Despite the fact that most of our information about solar flares was devised from analysis of observations obtained either in chromospheric emission lines or radio or EUV emission, the first ever observed solar flare was seen by a naked eye in the white light [@1859MNRAS..20...13C; @1859MNRAS..20...15H].

A class of white-light flares (WLF) is considered something special, where the true origin of the continuum emission is not entirely clear [see a recent overview by @2016SoPh..291.1273H]. The original idea was based on an assumption that in the strong flares, the electron beams penetrate all the way down into the photosphere, where they by collisions heat the photospheric plasma, which then radiates thermally. Recent simulations [such as by @2016AN....337.1020M] do not support this idea, because it seems that most of the energy in beams is deposited already at chromospheric levels and only a small fraction may propagate further down. [@2008ApJ...675.1645F] suggested an alternative model in which the energy is transported from the reconnection 