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arXiv · 2408.05725

Various Features of the X-class White-light Flares in Super Active Region NOAA 13664

Ying Li·Xiaofeng Liu·Zhichen Jing·Wei Chen·Qiao Li·Yang Su·De-Chao Song·M. D. Ding·Li Feng·Hui Li·Weiqun Gan
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Abstract

Super active region NOAA 13664 produced 12 X-class flares (including the largest one, an occulted X8.7 flare, in solar cycle 25 so far) during 2024 May 8-15 and 11 of them are identified as white-light flares. Here we present various features of these X-class white-light flares observed by the White-light Solar Telescope (WST) on board the Advanced Space-based Solar Observatory and the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory. It is found that both the white-light emissions at WST 3600 Å (Balmer continuum) and HMI 6173 Å (Paschen continuum) show up in different regions of the sunspot group in these flares, including outside the sunspots and within the penumbra and umbra of the sunspots. They exhibit a point-, ribbon-, loop-, or ejecta-like shape, which can come from flare ribbons (or footpoints), flare loops, and plasma ejecta depending on the perspective view. The white-light duration and relative enhancement are measured and both parameters for 3600 Å emission have greater values than those for 6173 Å emission. It is also found that these white-light emissions are cospatial well with the hard X-ray (HXR) sources in the on-disk flares but have some offsets with the HXR emissions in the off-limb flares. In addition, it is interesting that the 3600 and 6173 Å emissions show different correlations with the peak HXR fluxes, with the former one more sensitive to the HXR emission. All these greatly help us understand the white-light flares of a large magnitude from a super active region on the Sun and also provide important insights into superflares on Sun-like stars.

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Ying Li, Xiaofeng Liu, Zhichen Jing, Wei Chen, Qiao Li, Yang Su, De-Chao Song, M. D. Ding, Li Feng, Hui Li, Weiqun Gan. 2024-08-11. Various Features of the X-class White-light Flares in Super Active Region NOAA 13664. https://arxiv.org/abs/2408.05725

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