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arXiv 2410.02585astro-ph.SR
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日冕暗化的恢复

Recovery of coronal dimmings

Giulia M. Ronca, Galina Chikunova, Karin Dissauer, Tatiana Podladchikova, Astrid M. Veronig

AI总结:

本文提出固定掩模和像素盒两种方法,通过四个耀斑/CME案例研究日冕暗化的长期恢复过程,发现亮度恢复呈两阶段趋势,核心暗化与次级暗化具有不同恢复时间尺度,并证明日冕环膨胀是主要恢复机制。

摘要:

日冕暗化是日冕物质抛射(CME)发生后在低日冕中观测到的辐射减弱区域,代表了CME的足点。为了研究日冕暗化的长期演化及其恢复过程,我们提出了两种方法,分别关注暗化区域的全局演化和局部演化:固定掩模方法和像素盒方法。我们展示了四个案例研究(2011年9月6日、2012年3月7日、2012年6月14日和2019年3月8日),其中日冕暗化与耀斑/CME爆发相关联。我们通过图像分割识别暗化区域,然后将分析限制在暗化的特定部分,并跟踪暗化亮度和面积的时间演化。此外,我们研究了暗化区域内部约3×3像素的小子区域的行为,以比较暗化不同区域的恢复情况。四个案例中有三个在耀斑/CME爆发24小时后显示出完全恢复。亮度的恢复遵循两阶段趋势,先是一个更陡峭、更快速的阶段,随后是一个较慢的阶段。此外,暗化的某些部分(可能是核心暗化)在分析时间结束时仍然存在,并且在3天内没有恢复,而外围区域(次级暗化)则显示出完全恢复。我们证明,观测中识别出的主要恢复机制是日冕环向暗化区域的膨胀,这些日冕环的强度逐渐增加。我们开发的方法能够在这些明亮结构旁边分析暗化,揭示核心暗化区域和次级/孪生暗化区域具有不同的恢复时间尺度。结合磁场建模,这些方法为进一步系统分析暗化恢复奠定了基础,并增强了从已分析事件中获得的知识。

英文摘要:

Coronal dimmings are regions of reduced emission in the lower corona, observed after coronal mass ejections (CMEs) and representing their footprints. In order to investigate the long-term evolution of coronal dimming and its recovery, we propose two approaches that focus on both the global and the local evolution of dimming regions: the fixed mask approach and the pixel boxes approach. We present four case studies (September 6, 2011; March 7, 2012; June 14, 2012; and March 8, 2019) in which a coronal dimming is associated with a flare/CME eruption. We identified the dimming region by image segmentation, then restricted the analysis to a specific portion of the dimming and tracked the time evolution of the dimming brightness and area. In addition, we studied the behavior of small subregions inside the dimming area, of about 3x3 pixels, to compare the recovery in different regions of the dimming. Three out of the four cases show a complete recovery 24 hours after the flare/CME eruption. The recovery of the brightness follows a two-step trend, with a steeper and quicker segment followed by a slower one. In addition, some parts of the dimming, which may be core dimmings, are still present at the end of the analysis time and do not recover within 3 days, whereas the peripheral regions (secondary dimmings) show a full recovery. We demonstrate that the primary mechanism for recovery identified in the observations is the expansion of coronal loops into the dimming region, which gradually increase their intensity. Our developed approaches enable the analysis of dimmings alongside these bright structures, revealing different timescales of recovery for core and secondary/twin dimming regions. Combined with magnetic field modeling, these methods lay the foundation for further systematic analysis of dimming recovery and enhance the knowledge gained from already-analyzed events.

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