Scaling of Electron Heating by Magnetization During Reconnection and Applications to Dipolarization Fronts and Super‐Hot Solar Flares
Scaling of Electron Heating by Magnetization During Reconnection and Applications to Dipolarization Fronts and Super‐Hot Solar Flares
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DOI：
10.1029/2022ja030610
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发表时间：
2022-08
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影响因子：
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通讯作者：
M. H. Barbhuiya;P. Cassak;M. Shay;V. Roytershteyn;M. Swisdak;A. Caspi;A. Runov;Haoming Liang
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作者：
M. H. Barbhuiya;P. Cassak;M. Shay;V. Roytershteyn;M. Swisdak;A. Caspi;A. Runov;Haoming Liang
电子环速度空间分布之前已经在磁重联排气的数值模拟中看到，并且被认为是由压缩的重联磁场对电子流出射流的磁化引起的（Shuster et al., 2014, https://doi.org/10.1002/2014GL060608）。我们提出了环分布的主要半径和次要半径仅依赖于上游（瓣）等离子体条件的理论，从而允许根据上游参数预测环的相关温度和温度各向异性。我们使用改变上游等离子体密度和温度的2.5维粒子池（PIC）模拟来测试预测的有效性，发现预测值和模拟值之间非常吻合。我们证实了Shuster等人关于环分布原因的建议，并发现环分布位于重联磁场剖面中以高原或肩为标志的区域。对温度的预测与观测到的双极化前沿电子温度一致，并可能为在超热太阳耀斑中产生温度在10 MK左右的等离子体提供解释。讨论了将该模型推广到日侧重连的可能性。由于已知环分布会激发哨声波，因此本研究结果将有助于量化重连排气中哨声波的产生。
Electron ring velocity space distributions have previously been seen in numerical simulations of magnetic reconnection exhausts and have been suggested to be caused by the magnetization of the electron outflow jet by the compressed reconnected magnetic fields (Shuster et al., 2014, https://doi.org/10.1002/2014GL060608). We present a theory of the dependence of the major and minor radii of the ring distributions solely in terms of upstream (lobe) plasma conditions, thereby allowing a prediction of the associated temperature and temperature anisotropy of the rings in terms of upstream parameters. We test the validity of the prediction using 2.5‐dimensional particle‐in‐cell (PIC) simulations with varying upstream plasma density and temperature, finding excellent agreement between the predicted and simulated values. We confirm the Shuster et al. suggestion for the cause of the ring distributions, and also find that the ring distributions are located in a region marked by a plateau, or shoulder, in the reconnected magnetic field profile. The predictions of the temperature are consistent with observed electron temperatures in dipolarization fronts, and may provide an explanation for the generation of plasma with temperatures in the 10s of MK in super‐hot solar flares. A possible extension of the model to dayside reconnection is discussed. Since ring distributions are known to excite whistler waves, the present results should be useful for quantifying the generation of whistler waves in reconnection exhausts.