site to the very deep layers of solar atmosphere by Alvén-wave pulses, which would provide an environment for the electrons in the lower atmosphere to be efficiently accelerated to high energies. Those accelerated electrons then collisionally stimulate the white-light (WL) emission.

It was found that the WL emission correlates well with hard X-ray sources , which would indicate that the source region of the WL emission is in the low chromosphere. In case of a 30 Sep 2002 flare the kernels of a continuum emission even moved cospatially with the X-ray footpoints [@2006ApJ...641.1217C] indicating that the source term for the emission must be the collisions by non-thermal electrons. [@2016RAA....16..177H] demonstrated by studying a set of 13 WLFs that stronger WL emission tends to be associated with a larger population of high energy electrons. A similar study by [@2016ApJ...816....6K] indicated that for the WL production, flare-accelerated electrons of energy $\sim50$ keV are the main source. [@2007ApJ...656.1187F] on the contrary pointed out that the bulk of the energy required to power the WLF resides at lower energies of around 25 keV. A thorough study of X1 flare [@2017ApJ...836...12K] showed that the emission may originate from two layers in the atmosphere, the dense 