Implications for Additional Plasma Heating Driving the Extreme-ultraviolet Late Phase of a Solar Flare with Microwave Imaging Spectroscopy
Implications for Additional Plasma Heating Driving the Extreme-ultraviolet Late Phase of a Solar Flare with Microwave Imaging Spectroscopy
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DOI：
10.3847/1538-4357/ac6ce3
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发表时间：
2022-05
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影响因子：
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通讯作者：
Jiale Zhang;Bin Chen;Sijie Yu;H. Tian;Yuqian Wei;Hechao Chen;Guangyu Tan;Yingjie Luo;Xingyao Chen
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文献类型：
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作者：
Jiale Zhang;Bin Chen;Sijie Yu;H. Tian;Yuqian Wei;Hechao Chen;Guangyu Tan;Yingjie Luo;Xingyao Chen
极紫外后期（ELP）是指在某些太阳耀斑中观测到的第二次极紫外（EUV）辐射增强，通常发生在软x射线发射峰值后的数十分钟至数小时。承载ELP发射的日冕环系统通常不同于主燃烧拱廊，其中增强的EUV发射可能意味着额外的加热过程。然而，ELP的起源仍然相当不清楚。在这里，我们展示了一个C1.4耀斑的分析，它具有这样的ELP，它也被扩展欧文斯谷太阳能阵列在微波波长中观测到。与ELP的情况类似，我们发现在主脉冲相位微波峰值后约3分钟出现了逐渐的微波增强。射电源与ELP回路的两个足点重合，而随时间变化的微波谱的谱拟合表明电子分布明显偏离麦克斯韦情况，这可能是由于注入了非热电子或对足点等离子体的不均匀加热造成的。我们进一步指出，延迟的微波增强表明存在额外的加热过程，这可能是导致填充ELP环的加热等离子体蒸发的原因，从而产生延长的ELP发射。
Extreme-ultraviolet late phase (ELP) refers to the second extreme-ultraviolet (EUV) radiation enhancement observed in certain solar flares, which usually occurs tens of minutes to several hours after the peak of soft X-ray emission. The coronal loop system that hosts the ELP emission is often different from the main flaring arcade, and the enhanced EUV emission therein may imply an additional heating process. However, the origin of the ELP remains rather unclear. Here we present the analysis of a C1.4 flare that features such an ELP, which is also observed in microwave wavelengths by the Expanded Owens Valley Solar Array. Similar to the case of the ELP, we find a gradual microwave enhancement that occurs about 3 minutes after the main impulsive phase microwave peaks. Radio sources coincide with both foot points of the ELP loops and spectral fits on the time-varying microwave spectra demonstrate a clear deviation of the electron distribution from the Maxwellian case, which could result from injected nonthermal electrons or nonuniform heating to the footpoint plasma. We further point out that the delayed microwave enhancement suggests the presence of an additional heating process, which could be responsible for the evaporation of heated plasma that fills the ELP loops, producing the prolonged ELP emission.