Observation and theory of Pc 5 waves with harmonically related transverse and compressional components
Observation and theory of Pc 5 waves with harmonically related transverse and compressional components
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具有谐波相关横向和压缩分量的 Pc 5 波的观测和理论
DOI：
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发表时间：
1990
期刊：
影响因子：
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通讯作者：
L. Kistler
中科院分区：
文献类型：
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作者：
Kazue Takahashi;C. Cheng;R. Mcentire;L. Kistler
研究了AMPTE CCE宇宙飞船观测到的23个磁脉动事件的性质。这些事件是根据在同时存在的横向振荡的二次谐波处振荡的场强来选择的。这些事件的二次谐波周期为80 - 600s（大致为pc5范围），在黎明（0300-0800磁地方时，MLT）和黄昏（1600-2100 MLT）扇区中观测到，并且定位在磁赤道附近。虽然根据离子有限拉莫尔半径效应估计的方面波数m通常很大（|m| ~ 50），但在黎明和黄昏扇区观测到的事件之间存在显著差异。在黎明扇区，波的频率较低（1-5兆赫），相对于周围的磁场表明左极化，并相对于航天器向东传播。在黄昏区域，波具有高频率（5-15兆赫），指示右侧偏振，并向西传播。我们认为波在等离子体静止坐标系中都是向西传播的，局地时相关的多普勒频移是波特性局地时相关的原因。漂移镜不稳定性被认为是激发向西传播波的机制。在非线性陀螺动力学理论的基础上，导出了离子通量振荡的解析公式。离子通量与平行磁场扰动δB∥之间的关系可以用该解析式充分解释。
The properties of 23 magnetic pulsation events observed by the AMPTE CCE spacecraft are studied. These events are selected on the basis of the field magnitude which oscillated at the second harmonic of a simultaneously present transverse oscillation. The events have a second harmonic period of 80–600 s (roughly the Pc 5 range), are observed in cluster in the dawn (0300–0800 magnetic local time, MLT) and dusk (1600–2100 MLT) sectors, and are localized near the magnetic equator. Although the azimuthal wave number, m, estimated from an ion finite Larmor radius effect, is generally large (|m| ∼ 50), there is a marked difference between the events observed in the dawn and dusk sectors. In the dawn sector the waves have low frequencies (1–5 mHz), indicate left-hand polarization with respect to the ambient magnetic field, and propagate eastward with respect to the spacecraft. In the dusk sector the waves have high frequencies (5–15 mHz), indicate right-hand polarization, and propagate westward. We suggest that the waves are all westward propagating in the plasma rest frame and that local-time-dependent Doppler shift is the reason for the local time dependence of the wave properties. The drift mirror instability is considered to be the mechanism for exciting the westward propagating waves. An analytical formula for the ion flux oscillations is derived on the basis of the nonlinear gyrokinetic theory. The observed correlation between the ion flux and the parallel magnetic field perturbation δB∥ can be adequately explained with this analytical formula.