利用HARPS-N观测的两次X2.2级与X9.3级太阳耀斑的比较研究：在太阳-恒星联系背景下调和“太阳作为恒星”光谱学与高空间分辨率太阳观测
A comparative study of two X2.2 and X9.3 solar flares observed with HARPS-N: Reconciling Sun-as-a-star spectroscopy and high-spatial resolution solar observations in the context of the solar-stellar connection
AI总结：
本研究利用HARPS-N观测两次不同强度的太阳耀斑，结合高分辨率空间观测分析盘积分光谱特征，揭示了耀斑位置与光谱剖面的关联及多种谱线的活动响应规律，为恒星耀斑研究提供参考。
摘要：
恒星耀斑无法进行空间分辨，这使得确定特定光谱特征背后的物理过程变得复杂。由于太阳耀斑距离地球较近，它们可作为理解恒星耀斑的垫脚石，尤其是在使用“太阳作为恒星”仪器并结合空间分辨观测的情况下。我们旨在了解由HARPS-N（高精度径向速度行星搜索器-北天）测量的一次受限X2.2级太阳耀斑及其后续爆发的X9.3级耀斑的盘积分光谱行为。我们通过活动指数和对比度剖面研究了多条光球和色球谱线的行为。我们还通过等效宽度和径向速度测量研究了多种不同的光球谱线，并将这些结果与瑞典1米太阳望远镜和SDO（太阳动力学天文台）高分辨率观测中直接观测到的物理过程相关联。我们的研究结果表明，对比度剖面时间的演化形状与耀斑位置之间存在关联，这有助于在盘积分观测中约束耀斑位置。此外，我们发现基于Ca II H&K线推导的活动指数的耀斑统计存在向上偏差。在这种情况下，小得多的耀斑引起的活动指数增加与较大耀斑产生的增加相似。基于Hα的活动指数未表现出这种偏差，因此不易受活动抖动的影响。钠线剖面在耀斑活动期间表现出强烈的不对称响应，这一响应通过新定义的不对称钠活动指数得到了最佳捕捉。我们在Mn I线剖面中检测到强烈的耀斑响应，这一结果出乎意料，需要进一步探索。Hα、Hβ以及AIA（大气成像组件）的某些光谱窗口在耀斑开始前的强度增加表明它们有潜力用作短期耀斑预测因子。
英文摘要：
Stellar flares cannot be spatially resolved, which complicates ascertaining the physical processes behind particular spectral signatures. Due to their proximity to Earth, solar flares can serve as a stepping stone for understanding their stellar counterparts, especially when using a Sun-as-a-star instrument and in combination with spatially resolved observations. We aim to understand the disk-integrated spectral behaviors of a confined X2.2 solar flare and its eruptive X9.3 successor as measured by HARPS-N. The behavior of multiple photospheric and chromospheric spectral lines are investigated by means of activity indices and contrast profiles. A number of different photospheric lines were also investigated by means of equivalent widths, and radial velocity measures, which are then related to physical processes directly observed in high-resolution observations made with the Swedish 1-meter Solar Telescope and SDO Our findings suggest a relationship between the evolving shapes of contrast profile time and the flare locations, which assists in constraining flare locations in disk-integrated observations. In addition, an upward bias was found in flare statistics based on activity indices derived from the Ca II H & K lines. In this case, much smaller flares cause a similar increase in the activity index as that produced by larger flares. H$α$-based activity indices do not show this bias and are therefore less susceptible to activity jitter. Sodium line profiles show a strongly asymmetric response during flare activity, which is best captured with a newly defined asymmetrical sodium activity index. A strong flare response was detected in Mn I line profiles, which is unexpected and calls for further exploration. Intensity increases in H$α$, H$β$, and certain spectral windows of AIA before the flare onset suggest their potential use as short-term flare predictors.
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