Dawn-Dusk Asymmetries in Planetary Plasma Environments
Dawn-Dusk Asymmetries in Planetary Plasma Environments
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DOI：
10.1002/9781119216346
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发表时间：
2017-10
期刊：
影响因子：
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通讯作者：
S. Haaland;A. Runov;C. Forsyth
中科院分区：
文献类型：
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作者：
S. Haaland;A. Runov;C. Forsyth
极光粒子降水表现出黎明-黄昏的不对称性，反映了磁层中粒子群、波和过程的不对称性。扩散极光电子主要在22：00-09：00 MLT期间观测到，这与哨声模式合唱波的大部分空间分布相吻合，哨声模式合唱波已被证明是俯仰角散射磁层电子进入损失锥的主要机制。另一方面，单能极光电子可以在黄昏-午夜扇区观察到。单能电子是磁层电子，它们在向上的场向电流区域中通过了准静态平行电场。宽带极光电子主要出现在MLT的22：00-02：00，在那里观测到Alfvén波坡印廷通量的峰值。阿尔文波已知会引起电子的宽带加速。单能电子和宽带电子之间可能存在联系，因为低频阿尔文波-电子相互作用可以导致单能电子签名。亚暴使弥散、单能和宽带电子极光的功率分别增加了310%、71%和170%。单能和宽带极光的亚暴周期持续时间约为5 h，而扩散极光电子的亚暴周期则大于5 h。
Auroral particle precipitation exhibits dawn‐dusk asymmetries that reflect the asymmetries in the particle populations, waves, and processes in the magnetosphere. The diffuse auroral electrons can be observed mainly in 22: 00–09: 00 MLT, which coincides with much of the spatial distribution of the whistler‐mode chorus waves that have been shown to be the predominant mechanism for pitch‐angle scattering magnetospheric electrons into the loss cone. On the other hand, the monoenergetic auroral electrons can be observed in the dusk‐midnight sector. The monoenergetic electrons are magnetospheric electrons that have gone through a quasistatic parallel electric field in the upward field‐aligned current regions. The broadband auroral electrons can be found mostly at 22: 00–02: 00 MLT where a peak in the Poynting flux of Alfvén waves is observed. Alfvén waves are known to cause broadband acceleration of electrons. There may be a connection between monoenergetic and broadband electrons in that the low‐frequency Alfvén wave–electron interaction can result in monoenergetic electron signature. Substorms increase the power of the diffuse, monoenergetic, and broadband electron aurora by 310%, 71%, and 170%, respectively. The duration of the substorm cycle for monenergetic and broadband auroral is~ 5 h, but it is larger than 5 h for diffuse auroral electrons.