Non-thermal broadening of IRIS Fe XXI line caused by turbulent plasma flows in the magnetic reconnection region during solar eruptions
Non-thermal broadening of IRIS Fe XXI line caused by turbulent plasma flows in the magnetic reconnection region during solar eruptions
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DOI：
10.3389/fspas.2023.1096133
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发表时间：
2022-11
期刊：
影响因子：
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通讯作者：
Chengcai Shen;V. Polito;K. Reeves;Bin Chen;Sijie Yu;Xiao-yang Xie
中科院分区：
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作者：
Chengcai Shen;V. Polito;K. Reeves;Bin Chen;Sijie Yu;Xiao-yang Xie
磁重联是太阳爆发过程中能量释放的关键机制，高温辐射是研究重联过程中等离子体特性的主要诊断手段。紫外光谱仪在重联电流片和耀斑环顶区域均观察到高温线的非热展宽，但其起源尚不清楚。在这项工作中，我们使用最近开发的三维磁流体动力学（MHD）模拟来模拟标准太阳耀斑几何中的磁重联，并揭示重联区域的高动态等离子体流动。利用界面区域成像光谱仪（IRIS）观测到的Fe XXI 1354 Å谱线的MHD模型参数，包括等离子体密度、温度和速度，计算了合成谱线的轮廓。我们的模型表明，CS和耀斑环顶区域的湍流体流是导致fexxi发射线非热展宽的原因。模拟的非热速度范围从几十km s - 1到超过200 km s - 1，与IRIS观测结果一致。重联区周围的二维谱线模拟图也显示了高非热速度较大的高动态下流结构，这与观测结果也一致。
Magnetic reconnection is the key mechanism for energy release in solar eruptions, where the high-temperature emission is the primary diagnostic for investigating the plasma properties during the reconnection process. Non-thermal broadening of high-temperature lines has been observed in both the reconnection current sheet (CS) and flare loop-top regions by UV spectrometers, but its origin remains unclear. In this work, we use a recently developed three-dimensional magnetohydrodynamic (MHD) simulation to model magnetic reconnection in the standard solar flare geometry and reveal highly dynamic plasma flows in the reconnection regions. We calculate the synthetic profiles of the Fe XXI 1354 Å line observed by the Interface Region Imaging Spectrograph (IRIS) spacecraft by using parameters of the MHD model, including plasma density, temperature, and velocity. Our model shows that the turbulent bulk plasma flows in the CS and flare loop-top regions are responsible for the non-thermal broadening of the Fe XXI emission line. The modeled non-thermal velocity ranges from tens of km s−1 to more than two hundred km s−1, which is consistent with the IRIS observations. Simulated 2D spectral line maps around the reconnection region also reveal highly dynamic downwflow structures where the high non-thermal velocity is large, which is consistent with the observations as well.