Extreme-ultraviolet fine structure and variability associated with coronal rain revealed by Solar Orbiter/EUI HRI EUV and SPICE
Extreme-ultraviolet fine structure and variability associated with coronal rain revealed by Solar Orbiter/EUI HRI EUV and SPICE
复制标题
太阳轨道飞行器/EUI HRI EUV 和 SPICE 揭示了与日冕雨相关的极紫外精细结构和变化
DOI：
10.1051/0004-6361/202346016
复制
发表时间：
2023
影响因子：
6.5
通讯作者：
Antolin P
中科院分区：
文献类型：
--
作者：
Antolin P
背景日冕雨是日冕最显着的冷却现象。最近对可见光和紫外线光谱的观察表明，日冕雨是活跃地区普遍存在的现象。它通过热非平衡（TNE）-热不稳定（TI）情景与日冕加热密切相关，使其成为加热特性的重要诊断工具。除了加热之外，日冕的另一个令人费解的特征是它的丝状结构和变异性，特别是在极端紫外线（EUV）中。目的我们的目标是在小和大空间尺度上识别日冕雨下的 TNE-TI 场景的可观测特征，以了解它在日冕中所扮演的角色。方法我们使用来自极紫外（HRIEUV）高分辨率成像仪（HRI）的前所未有的空间分辨率约 240 公里的 EUV 数据集2022 年 3 月和 4 月，太阳轨道飞行器上的紫外线成像仪 (EUI) 和 SPICE 在近日点拍摄。结果在小至 260 公里的尺度上检测到了日冕雨产生的 EUV 吸收特征。当降雨时，下游立即产生加热和压缩，导致伴随降雨的小幅 EUV 增亮，并在日冕中产生火球现象。就在撞击之前，观测到雨下游出现类似闪光的 EUV 变亮，持续几分钟，这是最快的事件。我们第一次检测到大气对降雨对色球层影响的反应，它由向上传播的反弹冲击和流动组成，部分地重新加热了环路。观测到的雨团宽度为500±200公里。它们表现出 10 − 150 km s−1 的广泛速度分布，峰值低于 50 km s−1。沿着相同的环观察到相似宽度的冠状链。它们与 SPICE 中看到的冷丝状结构共空间，我们将其解释为凝结日冕过渡区域。在降雨出现之前，在从日冕温度到色球温度逐渐变冷的线路中检测到连续的环路增亮。这符合预期的冷却。尽管有大量阵雨，但大多数阵雨在 AIA 171 中无法被正交检测到，这表明视线效应在日冕雨的可见度中起着重要作用。 AIA 304 和 SPICE 观测结果仍然表明，HRIEUV 只能捕获一小部分降雨。结论日冕雨在从日冕环到最小可解析尺度的各种尺度上产生 EUV 结构和变化。这确立了 TNE-TI 在观测到的 EUV 形态和日冕变化中发挥的主要作用。
ContextCoronal rain is the most dramatic cooling phenomenon of the solar corona. Recent observations in the visible and UV spectrum have shown that coronal rain is a pervasive phenomenon in active regions. Its strong link with coronal heating through the thermal non-equilibrium (TNE) – thermal instability (TI) scenario makes it an essential diagnostic tool for the heating properties. Another puzzling feature of the solar corona in addition to the heating is its filamentary structure and variability, particularly in the extreme UV (EUV).AimsWe aim to identify observable features of the TNE-TI scenario underlying coronal rain at small and large spatial scales to understand the role it plays in the solar corona.MethodsWe used EUV datasets at an unprecedented spatial resolution of ≈240 km from the High Resolution Imager (HRI) in the EUV (HRIEUV) of the Extreme Ultraviolet Imager (EUI) and SPICE on board Solar Orbiter from the perihelion in March and April 2022.ResultsEUV absorption features produced by coronal rain are detected at scales as small as 260 km. As the rain falls, heating and compression is produced immediately downstream, leading to a small EUV brightening that accompanies the fall and produces a fireball phenomenon in the solar corona. Just prior to impact, a flash-like EUV brightening downstream of the rain, lasting a few minutes, is observed for the fastest events. For the first time, we detect the atmospheric response to the impact of the rain on the chromosphere, and it consists of upward-propagating rebound shocks and flows that partly reheat the loop. The observed widths of the rain clumps are 500 ± 200 km. They exhibit a broad velocity distribution of 10 − 150 km s−1and peak below 50 km s−1. Coronal strands of similar widths are observed along the same loops. They are co-spatial with cool filamentary structure seen with SPICE, which we interpret as the condensation corona transition region. Prior to the appearance of the rain, sequential loop brightenings are detected in gradually cooler lines from coronal to chromospheric temperatures. This matches the expected cooling. Despite the large rain showers, most cannot be detected in AIA 171 in quadrature, indicating that line-of-sight effects play a major role in the visibility of coronal rain. The AIA 304 and SPICE observations still reveal that only a small fraction of the rain can be captured by HRIEUV.ConclusionsCoronal rain generates EUV structure and variability over a wide range of scales, from coronal loops to the smallest resolvable scales. This establishes the major role that TNE-TI plays in the observed EUV morphology and variability of the corona.