| Presentation Title: | Sun-as-a-star Analysis of the X1.6 Flare on 2023 August 5: Dynamics of Post-flare Loops in Spatially Integrated Observational Data |
| Author(s): | Takato Otsu, Ayumi Asai, Kai Ikuta, and Kazunari Shibata |
Abstract:
Post-flare loops are loop-like plasmas observed during the decay phase of typical solar flares. Recently, superflares, which emit energy more than 1033 erg, have been discovered in various stars (e.g., Maehara+ 2012), and many observations suggest that their basic mechanism is similar to that of solar flares. For example, filament/prominence eruptions, fundamental elements of standard solar flares as well as post-flare loops, have also been observed with superflares (Namekata+ 2022, 2023). These results are supported by the similarity with the spatially integrated solar data obtained by Sun-as-a-star analyses (Otsu+ 2022). However, the spatially integrated data of solar post-flare loops have not been fully investigated, and it is not yet clear how post-flare loops are observed in stellar cases.
To clarify behaviors of post-flare 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, ~ 107 K), SDO/AIA (EUV, ≥105 K) and SMART/SDDI at Hida Observatory, Kyoto University (Hα, ∼104 K), focusing on post-flare loops. As a result, this flare showed signatures corresponding to the important dynamics of the post-flare loops even in the spatially integrated data: (1) Cooling of post-flare loops was confirmed as peak time difference in soft X-rays, EUV, and Hα. Notably, the Hα light curve showed two distinct peaks corresponding to the flare ribbons and the post-flare loops. (2) Downflows were confirmed as simultaneous red/blue-shifted absorptions in Sun-as-a-star Hα spectra. (3) Apparent rise of post-flare loops was confirmed as the stop of the decay for the Hα light curve. These results are keys to detect stellar post-flare 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.