Detection of a Magnetic Discontinuity in the Upper Solar Chromosphere Associated with a Coronal Loop Brightening Observed by CLASP2.1 The Astrophysical Journal

We report the first detection of a magnetic discontinuity in the upper solar chromosphere associated with a coronal loop brightening. Our findings are based on novel observations obtained by the Chromospheric LAyer SpectroPolarimeter (CLASP2.1) suborbital space experiment. During its short 6 minute flight, CLASP2.1 successfully obtained spectropolarimetric data across the Mg ii h and k lines, which allowed us to map the longitudinal magnetic field at multiple heights in the chromosphere of a solar active region. During our observation, we found a coronal loop brightening that was intermittently and recurrently heated. The temperature of the brightening plasma is above 2.5 MK, which is higher than the ambient temperature, and no corresponding brightening is detected in the images of the photosphere and lower chromosphere. The notable finding of our study is that the coronal loop brightening of interest is observed across a region where the magnetic field polarity changes abruptly in the upper chromosphere. Our results provide observational evidence that the heating mechanism of the coronal loop brightening is consistent with magnetic reconnection in the upper solar chromosphere.

我们首次报道了太阳上层色球层中与冕环增亮相关的磁场间断面的探测成果。本研究的观测数据源自色球层光谱偏振仪（Chromospheric LAyer SpectroPolarimeter, CLASP2.1）亚轨道空间实验获取的全新观测资料。在仅持续6分钟的短暂飞行任务中，CLASP2.1成功获取了覆盖镁II（Mg II）H、K谱线的光谱偏振数据，借此我们得以对某一太阳活动区色球层多个高度处的纵向磁场进行成像测绘。观测期间，我们发现一处存在间歇性反复加热现象的冕环增亮结构：该增亮等离子体的温度超过2.5兆开尔文（MK），高于周围环境温度，且在光球层与下层色球层的成像数据中未探测到对应的增亮信号。本研究的核心发现为，目标冕环增亮结构所处的上层色球层区域内，磁场极性发生了突变。本研究结果为冕环增亮的加热机制与太阳上层色球层中的磁场重联相一致提供了观测证据。