Heating Effects of Supra-arcade Downflows on Plasma above Solar Flare Arcades
Heating Effects of Supra-arcade Downflows on Plasma above Solar Flare Arcades
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DOI：
10.3847/1538-4357/ac9f47
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发表时间：
2023-01
期刊：
影响因子：
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通讯作者：
Xiao-yang Xie;K. Reeves
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作者：
Xiao-yang Xie;K. Reeves
我们特意选择了三个耀斑来研究超拱廊下流（SADs）对周围风扇等离子体的加热效应。先前的研究发现，在一个耀斑中，大多数SADs周围的等离子体倾向于升温或保持相同的温度，伴随着可识别的特征，即由于等离子体压缩而产生的绝热加热，以及由于等离子体粘性运动而产生的粘性加热。我们将这项工作扩展到更多的耀斑，发现SADs的加热效应也存在于这些事件中。在每个过程中，绝热加热都占主导地位。两个M1.3耀斑的绝热加热在0.02 ~ 0.18 MK s−1量级，是相当可比的。在能量更高的X1.7耀斑中，绝热加热约为0.02-0.3 MK s−1，在此期间，我们观察到更明显的温度升高，数十个SADs通过风扇下降。由于SADs不断地加热周围的风扇等离子体，因此SADs经过的区域往往比没有SADs的区域冷却得慢得多，并且温度较高的等离子体最终集中在SADs经常经过的区域。我们还发现，没有SADs的区域的冷却速率为~ 1000 K s−1，比正常导电冷却的预期速度要慢得多。相反，冷却速率可以很好地解释为导电冷却被湍流抑制的过程。
We deliberately select three flares to investigate heating effects of supra-arcade downflows (SADs) on the surrounding fan plasma. Prior work found in one flare that the plasma around most SADs tends to heat up or stay the same temperature, accompanied by discernible signatures of the adiabatic heating due to plasma compression as well as viscous heating due to viscous motions of plasma. We extend this work to more flares and find that the heating effects of the SADs are also present in these events. The adiabatic heating is dominant over the viscous heating in each event. The adiabatic heating in the two M1.3 flares, being on the order of about 0.02–0.18 MK s−1, is fairly comparable. In the more energetic X1.7 flare, the adiabatic heating is on the order of 0.02–0.3 MK s−1, where we observe a more pronounced temperature increase during which dozens of SADs descend through the fan. As SADs constantly contribute to the heating of the surrounding fan plasma, the areas where SADs travel through tend to cool much slower than the areas without SADs, and the plasma of higher temperature ends up concentrating in areas where SADs frequently travel through. We also find that the cooling rate of areas without SADs is ∼1000 K s−1, much slower than would be expected from normal conductive cooling. Instead, the cooling rate can be interpreted nicely by a process where conductive cooling is suppressed by turbulence.