短曝光极紫外成像揭示的耀斑精细结构及其能量意义
Fine-scale flare structures and their energetic implications from short-exposure extreme-ultraviolet imaging
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中文总结 AI 辅助
该研究利用太阳轨道器HRIEUV短曝光观测结合STIX数据，揭示了耀斑致密精细结构，发现其足点面积远小于常规观测结果，为耀斑局部能流研究提供了关键约束。
中文摘要 AI 辅助
为捕捉太阳耀斑最明亮且演化最快的阶段，大型耀斑太阳轨道器观测计划为极紫外成像仪的174埃高分辨率成像仪（HRIEUV）采用了专用短曝光模式。我们利用高时间分辨率、短曝光的HRIEUV观测数据，研究2024年3月19日M2.1级耀斑中致密辐射的时空组织特征。我们将这些0.04秒分辨率的观测结果与X射线成像光谱仪（STIX）的硬X射线计时、成像及光谱数据相结合，对脉冲型 ribbon 核与后续环带结构进行表征，并对比HRIEUV、大气成像组件（AIA）及STIX测量的足点面积，以约束耀斑加速电子携带的局部能流。短曝光观测揭示了常规曝光极紫外成像中因饱和而被大量掩盖的致密辐射。HRIEUV的积分辐射演化与STIX的22-45千电子伏辐射同步，在2秒采样间隔内未发现可辨识延迟。耀斑 ribbon 包含反复激活的核，其特征间距约为1.4-1.7兆米，而发展中的环带显示出约1.3兆米的相似丝状物间距。核与丝状物的宽度约为0.4-0.5兆米，接近仪器分辨率极限。HRIEUV测得的致密足点面积比AIA或STIX推断的小约一个数量级，意味着硬X射线峰值处的局部非热能流约为10^11尔格·厘米^-2·秒^-1。这些结果揭示了耀斑辐射具有1-2兆米的特征空间组织，并证明了优化耀斑观测的极紫外成像对未来太阳耀斑观测的重要价值。
英文摘要
To capture the brightest and most rapidly evolving phases of solar flares, the Major Flare Solar Orbiter Observing Plan employed a dedicated short-exposure mode for the High Resolution Imager at 174 Angstrom (HRIEUV) of the Extreme Ultraviolet Imager. We investigate the spatial and temporal organisation of compact emission in the 19 March 2024 M2.1 flare using high-cadence, short-exposure HRIEUV observations. We combine these 0.04 s observations with hard X-ray timing, imaging, and spectroscopy from the Spectrometer Telescope for Imaging X-rays (STIX). We characterise impulsive ribbon kernels and later loop strands, and compare footpoint areas measured with HRIEUV, the Atmospheric Imaging Assembly, and STIX to constrain the local energy flux carried by flare-accelerated electrons. The short-exposure observations reveal compact emission largely obscured by saturation in normal-exposure EUV imaging. The integrated HRIEUV emission evolves co-temporally with the STIX 22-45 keV emission, with no lag discernible beyond the 2 s sampling. The ribbons comprise repeatedly activated kernels with characteristic separations of approximately 1.4-1.7 Mm, while the developing arcade shows a similar strand separation of approximately 1.3 Mm. Kernel and strand widths of approximately 0.4-0.5 Mm lie close to the instrumental resolution limit. The compact HRIEUV footpoint areas are approximately an order of magnitude smaller than those inferred from AIA or STIX, implying nominal local non-thermal energy fluxes on the order of 10^11 erg cm^-2 s^-1 at the hard X-ray peaks. These results reveal a characteristic 1-2 Mm spatial organisation of the flare emission and demonstrate the value of flare-optimised EUV imaging for future solar flare observations.
