  To understand the conditions that produce white-light (WL) enhancements in
solar flares, a statistical analysis of visible continuum data as observed by
Hinode/Solar Optical Telescope (SOT) was performed. In this study,
approximately 100 flare events from M- and X-class flares were selected. The
time period during which the data were recorded spans from January 2011 to
February 2016. Of these events, approximately half are classified as
white-light flares (WLFs), whereas the remaining events do not show any
enhancements of the visible continuum (non-WLF; NWL). In order to determine the
existence of WL emission, running difference images of not only the Hinode/SOT
WL (G-band, blue, green, and red filter) data but also the Solar Dynamics
Observatory/Helioseismic and Magnetic Imager continuum data are used. A
comparison between these two groups of WL data in terms of duration,
temperature, emission measure of GOES soft X-rays, distance between EUV flare
ribbons, strength of hard X-rays, and photospheric magnetic field strength was
undertaken. In this statistical study, WLF events are characterized by a
shorter time-scale and shorter ribbon distance compared with NWL events. From
the scatter plots of the duration of soft X-rays and the energy of non-thermal
electrons, a clear distinction between WLF and NWL events can be made. It is
found that the precipitation of large amounts of accelerated electrons within a
short time period plays a key role in generating WL enhancements. Finally, it
was demonstrated that the coronal magnetic field strength in the flare region
is one of the most important factors that allow the individual identification
of WLF events from NWL events.
