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Statistical Characteristics of Electron Pitch Angle Distributions Inside the Magnetopasue Based on MMS Observations
Journal of Geophysical Research: Space Physics ( IF 2.8 ) Pub Date : 2020-10-02 , DOI: 10.1029/2020ja028291
Haimeng Li 1, 2 , Qianshui Peng 1, 2 , Rongxin Tang 1, 2, 3 , He Zhang 1 , Zhihong Zhong 1 , Xiaohua Deng 1 , Dedong Wang 4
Affiliation  

Electron pitch angle distributions (PADs) are very important to understand dynamics in the Earth's magnetosphere. Using observations of the Magnetospheric Multiscale (MMS) mission, we statistically investigate the characteristics of several types of electron PADs with energies of 200 eV to 2 keV (low energy) and 2–30 keV (energetic energy) inside the dayside magnetopause (L = 8 ∼ 13). For the low (energetic) energy level, the occurrence rates of pancake, flat‐top, butterfly, isotropy, cigar, and rolling‐pin distributions are as follows: 50.34% (45.20%), 17.92% (43.41%), 3.07% (7.28%), 4.34% (1.54%), 16.20% (1.20%), and 1.80% (0.06%), respectively. The pancake PAD is mainly located at lower L‐shells with a maximum rate near the noonside, but other types of electron PADs occur at higher L‐shells. In addition, the occurrence rate of the flat‐top PAD is nearly the same for different magnetic local time. The butterfly and rolling‐pin PADs occur in the afternoon side. The cigar PAD is mostly located in both the dawnside and duskside but is very scarce in the noonside. Furthermore, the relationships between these PADs and the solar wind dynamic pressure (Pdyn) are studied. For low‐energy electrons, the occurrence rate of the pancake distribution decreases, and that of the butterfly distribution increases with the enhancement of Pdyn. However, for energetic energy level, the occurrence rate of the pancake (butterfly) PAD does not clearly decrease (increase) with the enhancement of Pdyn at L ≤ 12. The statistical results reveal the important role of Pdyn in electron dynamics inside the magnetopause.

中文翻译:

基于MMS观测的透磁内部电子变桨角分布的统计特征。

电子俯仰角分布(PAD)对于了解地球磁层的动力学非常重要。利用对磁层多尺度(MMS)任务的观察,我们统计了日间磁层顶内能量为200 eV至2 keV(低能量)和2–30 keV(高能)的几种类型的电子PAD的特性(L  = 8至13)。对于低(能量)能级,煎饼,平顶,蝴蝶,各向同性,雪茄和rolling面杖分布的发生率如下:50.34%(45.20%),17.92%(43.41%),3.07% (7.28%),4.34%(1.54%),16.20%(1.20%)和1.80%(0.06%)。煎饼PAD主要位于较低的L壳在中午附近具有最大速率,但其他类型的电子PAD则出现在更高的L壳处。此外,在不同的磁性本地时间,平顶PAD的发生率几乎相同。蝶形PAD和rolling面杖PAD出现在下午。雪茄PAD主要位于黎明和黄昏,但在中午却很少。此外,研究了这些PAD与太阳风动压(P dyn)之间的关系。对于低能电子,随着P dyn的增加,薄煎饼分布的发生率降低,而蝶形分布的发生率升高。然而,对于精力充沛的能量水平,煎饼(蝴蝶)PAD的发生率并没有明确减少(增加)与增强P DYN大号 ≤12的统计结果显示中的重要作用P DYN在里面的电子动态磁停。
更新日期:2020-10-15
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