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arXiv · 2409.07630

Sun-as-a-star Analysis of the X1.6 Flare on 2023 August 5: Dynamics of Post-flare Loops in Spatially Integrated Observational Data

Takato Otsu·Ayumi Asai·Kai Ikuta·Kazunari Shibata
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Abstract

Post-flare loops are loop-like plasmas observed during the decay phase of solar flares, and they are expected to exist for stellar flares. However, it is unclear how post-flare loops are observed in stellar flares' 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 on 2023 August 5, using GOES X-ray flux ($\sim10^7$ K), extreme ultraviolet (EUV) images taken by Atmospheric Imaging Assembly onboard the Solar Dynamic Observatory ($\ge10^{4.9}$ K) and H$\alpha$ data taken by Solar Dynamics Doppler Imager on board the Solar Magnetic Activity Research Telescope at Hida Observatory, Kyoto University ($\sim10^4$ K). As a result, this flare showed signatures corresponding to the important dynamics of the post-flare loops even in the spatially integrated data: (1) The H$\alpha$ light curve showed two distinct peaks corresponding to the flare ribbons and the post-flare loops. The plasma cooling in the post-flare loops generated different peak times in soft X-rays, EUV, and H$\alpha$ light curves. (2) Downflows were confirmed as simultaneous redshifted/blueshifted absorptions in the H$\alpha$ spectra. (3) The apparent rise of post-flare loops was recognized as a slowing of the decay for the H$\alpha$ light curve. These results are keys to investigating stellar post-flare loops with spatially integrated data. We also discuss the dependence of our results on flare locations and their possible applications to stellar observations.

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Takato Otsu, Ayumi Asai, Kai Ikuta, Kazunari Shibata. 2024-09-11. Sun-as-a-star Analysis of the X1.6 Flare on 2023 August 5: Dynamics of Post-flare Loops in Spatially Integrated Observational Data. https://arxiv.org/abs/2409.07630

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