Response of dayside Pc 5 pulsations to substorm activity in the nighttime magnetosphere
Response of dayside Pc 5 pulsations to substorm activity in the nighttime magnetosphere
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DOI：
10.1029/ja086ia02p00733
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发表时间：
1981-02
影响因子：
--
通讯作者：
J. Samson;G. Rostoker
中科院分区：
文献类型：
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作者：
J. Samson;G. Rostoker
最近，利用ULF(1-20 MHz)波诊断磁层结构的可能性为Pc4，5磁脉动的研究提供了新的动力。在本文中，我们证明了接近中午的日侧Pc_(4，5)脉动的频谱可能会随着临近午夜的磁层亚暴的开始而发生显著的变化。白天Pc脉动对亚暴爆发的响应时间可以短至2-3分钟，这表明信息以阿尔芬速度量级的速度通过磁层传输。日侧脉动的特征响应是日侧极光椭圆形内站点的主要频率显著增加。我们的结果与Eather等人对日边极光的观察结合在一起。[1979]表明亚暴开始时伴随着部分环流中心的突然内移。我们认为，这种环电流运动引起磁层赤道面磁场的变化，从而导致观测到磁脉动的磁力线上的Alfven速度发生变化。根据本文报道的观测结果，讨论了Pc4，5脉动产生的可能机制。
The possibility of using ULF (1–20 mHz) waves to diagnose the structure of the magnetosphere has recently given new impetus to the study of Pc 4,5 magnetic pulsations. In this paper we demonstrate that the frequency spectrum of dayside Pc 4,5 pulsations near noon may be significantly altered in association with the onset of a magnetospheric substorm near midnight. The response time for the dayside Pc pulsations to a substorm onset can be as short as 2–3 min, suggesting information transfer across the magnetosphere at velocities of the order of the Alfven speed. The characteristic response of the dayside pulsations is a marked increase in the dominant frequency at stations inside the dayside auroral oval. Our results taken together with the observations of dayside auroras by Eather et al. [1979] suggest that substorm onsets are accompanied by a sudden inward motion of the center of the partial ring current. We propose that this ring current motion causes changes in the magnetic field in the equatorial plane of the magnetosphere that result in changes in the Alfven velocity on field lines where the magnetic pulsations are observed. Possible mechanisms for the generation of Pc 4,5 pulsations are discussed in the light of the observations reported in this paper.