Observations of kinetic scale field line resonances
Observations of kinetic scale field line resonances
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DOI：
10.1002/2013gl058507
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发表时间：
2014-01
影响因子：
5.2
通讯作者：
C. Chaston;J. Bonnell;J. Wygant;F. Mozer;S. Bale;K. Kersten;A. Breneman;C. Kletzing;W. Kurth;G. Hospodarsky;Charles W. Smith;E. MacDonald
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文献类型：
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作者：
C. Chaston;J. Bonnell;J. Wygant;F. Mozer;S. Bale;K. Kersten;A. Breneman;C. Kletzing;W. Kurth;G. Hospodarsky;Charles W. Smith;E. MacDonald
我们确定电磁场的变化，从货车艾伦探针的多普勒频移动力尺度Alfvénic场线共振的属性。这些变化是在注入高能等离子体到内磁层期间观察到的。这些波具有垂直于磁场的尺度大小，被确定为离子陀螺半径（ρi）的量级或更小。电场和磁场的交叉谱分析揭示了与电场和磁场比率的增强和降低相关的频率处的相变。建模表明，这些观测结果与场线共振的激发在垂直于磁场（k）延伸到k ρ i 1的波数范围内是一致的。这些波的振幅使得E/Bo <$Ωi/k <$（E、Bo和Ωi分别是波振幅、背景场强度和离子陀螺频率）导致离子退磁和加速通过波势的多次跃迁。
We identify electromagnetic field variations from the Van Allen Probes which have the properties of Doppler shifted kinetic scale Alfvénic field line resonances. These variations are observed during injections of energetic plasmas into the inner magnetosphere. These waves have scale sizes perpendicular to the magnetic field which are determined to be of the order of an ion gyro‐radius (ρi) and less. Cross‐spectral analysis of the electric and magnetic fields reveals phase transitions at frequencies correlated with enhancements and depressions in the ratio of the electric and magnetic fields. Modeling shows that these observations are consistent with the excitation of field‐line resonances over a broad range of wave numbers perpendicular to the magnetic field (k⊥) extending to k⊥ρi ≫ 1. The amplitude of these waves is such that E/Bo ≳ Ωi/k⊥ (E, Bo, and Ωi are the wave amplitude, background field strength, and ion gyro‐frequency, respectively) leading to ion demagnetization and acceleration for multiple transitions through the wave potential.