The M- and X-class White-light Flares in Super Active Region NOAA 13664/13697 Observed by ASO-S/LST/WST (2509.11029v1)

Abstract: Solar white-light flares (WLFs) have been observed since 1859, but their occurrence rate is not yet fully understood. The physical properties of WLFs in super active regions (SARs) are also well worth investigating. With full-disk images at 3600 {\AA} (in the Balmer continuum) from the White-light Solar Telescope (WST) on board the Advanced Space-based Solar Observatory, we here study the M- and X-class WLFs occurring in SAR NOAA 13664/13697 (a same region in two solar Carrington rotations) during May/June 2024. 48 WLFs at 3600 {\AA} are identified from 89 available samples with an occurrence rate of 53.9%, which is much higher than that (23.9%) of a longterm-continuous data set from October 2022 to May 2023 in our previous work (Jing et al. 2024). In particular, with an additional sample of over 730 M- and X-class flares from October 2022 to June 2024, we find that the occurrence rate of WLFs shows a good correlation with the solar cycle represented by sunspot counts. As regards the properties of the emission at 3600 {\AA}, the WLFs in SAR NOAA 13664/13697 have some different characteristics, say, a longer duration but a weaker relative enhancement and a smaller brightening area compared with the previous long-term-continuous sample. We also find that for WLFs in NOAA 13664/13697 the relation between the duration and energy at 3600 {\AA} is described by a power-law with index of 0.35, which is similar to the results found for superflares in Sun-like stars (Kowalski 2024). All these help us understand the solar WLFs in SARs and also provide important insights into the superflares on Sun-like stars.