Description
Postflare loops are important components of the standard flare model, and their existence has been suggested even in stellar flares. However, the spatially integrated data of postflare loops have not been fully investigated, and it is not yet clear how postflare loops are observed in stellar cases. To clarify behaviors of postflare loops in spatially integrated data, we performed the Sun-as-a-star analysis of the X1.6 flare that occurred near the northwest limb on 2023 August 5 using GOES (soft X-rays, $\sim10^7$ K), SDO/AIA (EUV, ≥$10^5$ K) and SMART/SDDI at Hida Observatory, Kyoto University (H$\alpha$, $\sim10^4$ K), focusing on postflare loops. As a result, this flare showed signatures corresponding to the important dynamics of the postflare loops even in the spatially integrated data: (1) Cooling of postflare loops was confirmed as peak time difference in soft X-rays, EUV, and H$\alpha$. Notably, the H$\alpha$ light curve showed two distinct peaks corresponding to the flare ribbons and the postflare loops. (2) Downflows were confirmed as simultaneous red/blue-shifted absorptions in Sun-as-a-star H$\alpha$ spectra. (3) Apparent rise of postflare loops was confirmed as the stop of the decay for the H$\alpha$ light curve. These results are keys to detect stellar postflare loops in multiwavelength observations and grasp their dynamics with spatially integrated data. We also discuss the dependence of our results on flare locations and its possible applications to stellar observations. Moreover, we mention the statistical study of postflare loops for further understanding of stellar flares.
