A new type of VLF emission triggered at low altitude in the subauroral region by Siple Station VLF transmitter signals
A new type of VLF emission triggered at low altitude in the subauroral region by Siple Station VLF transmitter signals
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Siple Station VLF发射机信号在亚极光区低空触发的新型VLF发射
DOI：
10.1029/ja090ia12p12183
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发表时间：
1985
影响因子：
--
通讯作者：
H. G. James
中科院分区：
文献类型：
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作者：
T. Bell;J. Katsufrakis;H. G. James
来自ISIS 2卫星的甚低频波数据揭示了一种新的现象，即观测到来自南极Siple站的VLF相干信号，当这些信号通过电离层和低空磁层向上传播到1400公里高度的卫星时，触发了一种新型的VLF发射。发射具有带限脉冲的形式，持续时间约为20-30毫秒。发射的带宽高达1 kHz，其幅度比触发信号高出20dB。这些辐射被认为是发射机信号触发的快速演变的准静电等离子体不稳定的结果。这种影响一般发生在发射机信号正好位于一段脉冲甚低频嘶嘶声的下方时，通常观测到的脉冲甚低频嘶嘶声发生在等离子体顶层的极光以下区域。脉冲VLF嘶嘶带在3-4 kHz范围内有一个较低的截止频率，似乎是著名的极光VLF脉冲嘶嘶带的亚极光延伸。这种现象可能是最近报道的光谱展宽效应的瞬时类似[Bell等人，1983b]，但其中的联系尚不清楚。在本文中，我们展示了这一新现象的例子，并描绘了它发生的条件。讨论了高能粒子的沉淀在产生这一现象中的作用。
VLF wave data from the ISIS 2 satellite has revealed the existence of a new phenomenon in which coherent VLF signals from the Siple Station, Antarctica, VLF transmitter are observed to trigger a new type of VLF emission as these signals propagate upward to the satellite at 1400 km altitude through the ionosphere and low-altitude magnetosphere. The emissions have the form of band-limited impulses of approximately 20–30 ms duration. The bandwidth of the emissions is as much as 1 kHz and their amplitude is as much as 20 dB above that of the triggering signal. The emissions are thought to be the result of a rapidly evolving quasi electrostatic plasma instability triggered by the transmitter signals. The effect occurs generally when the transmitter signals lie just below a band of impulsive VLF hiss which is commonly observed to occur in the subauroral region poleward of the plasmapause. The impulsive VLF hiss band has a lower cutoff frequency in the range 3–4 kHz and appears to be the subauroral extension of the well-known auroral VLF impulsive hiss Band. This phenomenon is possibly the transient analog of the recently reported spectral broadening effect [Bell et al., 1983b] but the connection is not clear. In the present paper we show examples of this new phenomenon and delineate the conditions under which it occurs. The role of precipitating energetic particles in producing the phenomenon is discussed.