Electron acceleration associated with the magnetic flux pileup regions in the near‐Earth plasma sheet: A multicase study
Electron acceleration associated with the magnetic flux pileup regions in the near‐Earth plasma sheet: A multicase study
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DOI：
10.1002/2016ja022406
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发表时间：
2016-05
期刊：
影响因子：
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通讯作者：
C. Tang;M. Zhou;Z. Yao;F. Shi
中科院分区：
文献类型：
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作者：
C. Tang;M. Zhou;Z. Yao;F. Shi
利用亚暴期间的事件时间历史和宏观尺度相互作用（THEMIS）观测，我们研究了近地等离子体层（X ~ -10 RE）磁通量堆积区（FPRs）中的电子加速度（<30 keV）。我们提出了与双极化锋和亚暴双极化有关的三例FRPs。根据磁场的特性，我们将磁场增强区定义为通常在双极化锋边界层附近观测到的具有显著斜坡的磁场。另一方面，增加的磁场没有明显的斜坡是FPR的其余部分。我们的结果表明，在MFER内部10-30 keV的电子中，betatron加速度占主导地位，而在FPR的其余部分中，费米加速度占主导地位。Betatron加速是由局域磁场的增强引起的，而Fermi加速则与磁力线长度的缩小有关。这些在近地彗尾fpr内部的加速电子在地球电子辐射带和亚暴的演化中发挥着潜在的重要作用。
Using the Time History of Events and Macroscale Interactions during Substorms (THEMIS) observations, we study electron acceleration (<30 keV) in the magnetic flux pileup regions (FPRs) in the near‐Earth plasma sheet (X ~ –10 RE). We present three cases of FRPs associated with dipolarization fronts and substorm dipolarization. Based on the characteristics of the magnetic field, we defined the magnetic field enhancement region (MFER) as the magnetic field with significant ramp that is usually observed near the dipolarization front boundary layer. On the other side, the increased magnetic field without a significant ramp is the rest of a FPR. Our results show that betatron acceleration dominates for 10–30 keV electrons inside the MFER, whereas Fermi acceleration dominates for 10–30 keV electrons inside the rest of the FPR. Betatron acceleration is caused by the enhancement of the local magnetic field, whereas Fermi acceleration is related to the shrinking length of magnetic field line. These accelerated electrons inside the FPRs in the near‐Earth tail play a potentially important role in the evolution of the Earth's electron radiation belt and substorms.