回落至低日冕的受扰日冕物质抛射（CME）物质观测
Observations of Disrupted CME Material Falling Back Into the Low Corona
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中文总结 AI 辅助
该研究利用SOHO、STEREO-A、SDO和VLA的观测数据，通过运动学阻力模型，观测到受扰CME物质回落至低日冕的现象，发现其可能有助于日冕雨的形成。
中文摘要 AI 辅助
我们利用SOHO、STEREO-A和SDO的观测数据，对部分物质回落至太阳的受扰日冕物质抛射（CME）开展实证研究。2024年8月16日世界时18:00，一个慢CME被一个更快的CME追上；第二个CME的一个“腿”裹挟了部分慢CME物质，使该CME形成了异常清晰的通量绳腿结构。我们通过甚大阵（VLA）在射电波段观测到该第二个CME，其法拉第旋转测量结果显示出明确的磁通量绳特征；后续当射电观测视线进入受扰CME物质富集的CME腿时，还观测到强烈的响应。在该腿之外，受扰CME的其余部分直接消失，取而代之的是大量小型喷流状下行流。我们在SDO的极紫外（EUV）图像中清晰观测到该等离子体回落至低日冕的证据，发生在CME受扰后约6-17小时，推断其下行速度V=-30 km/s。下行流存在明显的温度依赖性，最先在211波段被观测到，随后依次在193、171和304波段出现响应；这些下行流的速度远低于弹道下落的预期值，因此我们采用运动学阻力模型对其进行建模。在304波段，下行的CME物质触发了日冕雨活动，这表明来自高层日冕的下行流可能对更广泛的日冕雨形成有贡献。
英文摘要
We present an empirical study of a disrupted CME, parts of which fall back to the Sun, using observations from SOHO, STEREO-A, and SDO. At UT 18:00 on 2024 August 16, a slow CME is overtaken by a faster CME. A leg of the second CME carries part of the slower CME out with it, resulting in an unusually well-defined flux rope leg for this CME. This second CME is observed in radio by the VLA, with Faraday rotation measurements showing a clear magnetic flux rope signature. A strong response is also later seen when the radio-observed line of sight enters the CME leg enriched by material from the disrupted CME. Outside this leg, the rest of the disrupted CME simply disappears and is replaced by a large number of small jet-like downflows. We see clear evidence of this plasma falling back to the low corona in EUV images from SDO, roughly 6-17 hours after the CME is disrupted, with an inferred downward velocity of V=-30 km/s. There is a clear temperature dependence, with the downflows seen first in the 211 bandpass, followed successively by responses at 193, 171, and 304. The downflows are much slower than would be expected for a ballistic descent, so we model the downflows using a kinematic drag model. In the 304 bandpass, coronal rain activity is triggered by the downflowing CME material, suggesting that downflows from the upper corona could be contributing to coronal rain more generally.
