Nonequilibrium Ionization Modeling of Petschek-type Shocks in Reconnecting Current Sheets in Solar Eruptions
Nonequilibrium Ionization Modeling of Petschek-type Shocks in Reconnecting Current Sheets in Solar Eruptions
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DOI：
10.3847/1538-4357/aca6e7
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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;J. Raymond;N. Murphy
中科院分区：
文献类型：
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作者：
Chengcai Shen;J. Raymond;N. Murphy
当等离子体状态偏离电离平衡假设时，非平衡电离（NEI）是天体物理等离子体诊断的必要条件。在这项工作中，我们进行快速NEI计算结合磁流体动力学（MHD）模拟和分析的Petschek型磁重联电流片在太阳爆发的电离特性。我们的模拟揭示了Petschek型慢模冲击在经典的Spitzer热传导模型和传导通量限制的情况下。结果表明，在激波重联流出区和激波外围的热晕区普遍存在欠电离特征。偏离平衡电离强烈地依赖于等离子体密度。此外，这种偏离对可观察到的目标温度很敏感：高温铁离子受到NEI效应的强烈影响。欠电离也影响合成SDO/AIA强度，这表明重建的热重联电流片结构可能被显着低估的温度或表观宽度。我们还对经典太阳耀斑几何中的重联电流片进行了MHD-NEI分析。最后，我们发现在重联电流片的下尖端，向下流出碰撞闭合的磁回路，可以强烈地影响多个SDO/AIA带比沿着重联电流片的电位反转之间的欠电离和过电离状态。
Nonequilibrium ionization (NEI) is essentially required for astrophysical plasma diagnostics once the plasma status departs from the assumption of ionization equilibrium. In this work, we perform fast NEI calculations combined with magnetohydrodynamic (MHD) simulations and analyze the ionization properties of a Petschek-type magnetic reconnection current sheet during solar eruptions. Our simulation reveals Petschek-type slow-mode shocks in the classical Spitzer thermal conduction models and conduction flux-limitation situations. The results show that under-ionized features can be commonly found in shocked reconnection outflows and thermal halo regions outside the shocks. The departure from equilibrium ionization strongly depends on plasma density. In addition, this departure is sensitive to the observable target temperature: the high-temperature iron ions are strongly affected by the effects of NEI. The under-ionization also affects the synthetic SDO/AIA intensities, which indicates that the reconstructed hot reconnection current sheet structure may be significantly underestimated either for temperature or apparent width. We also perform an MHD-NEI analysis on the reconnection current sheet in the classical solar flare geometry. Finally, we show the potential reversal between the under-ionized and over-ionized states at the lower tip of reconnection current sheets where the downward outflow collides with closed magnetic loops, which can strongly affect multiple SDO/AIA band ratios along the reconnection current sheet.