Local time dependence of the frequency of Pi2 waves simultaneously observed at 5 low-latitude stations
Local time dependence of the frequency of Pi2 waves simultaneously observed at 5 low-latitude stations
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5个低纬站同时观测到的Pi2波频率的局地时间依赖性
DOI：
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发表时间：
2003
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通讯作者：
M. Nosé
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作者：
Desheng Han;T. Iyemori;Yu;Y. Sano;Fuxi Yang;Wansheng Li;M. Nosé
来自低纬度5个台站的一秒分辨率地磁数据（即，L = 1.2 ~ 1.6），研究了Pi 2脉动主频率的局域时间依赖性。我们分析了5个台站同时记录的183个Pi 2事件，并讨论了它们可能的产生机制。H（水平）分量的平均主频率在黎明侧比在黄昏侧高，并且在午夜后在03 LT左右显示出峰值，这证实了先前从单站数据中提出的LT依赖性（即，非同时观察）。然而，一些事件没有LT依赖性。对于在低纬度显示LT依赖性的事件，我们推断腔共振模式是一个合理的生成机制，但我们不排除等离子体层表面波模式的可能性，这也被建议。对于东西台同频事件，我们认为是空腔共振模式。D分量的平均主频率没有显示出任何明显的LT依赖性，并且只有大约20%的Pi 2s的H和D分量具有相同的频率，因此我们认为Pi 2s的H和D振荡是由不同的机制产生的。我们还发现，Pi 2脉动的不同部分的频率，即，脉动的前部和后部的主频率不同，并且后部的频率低于前部的频率。
One-second resolution geomagnetic data from 5 stations located at low-latitudes (i.e., L = 1.2 ~ 1.6) were used to examine the local time dependence of the dominant frequency of Pi2 pulsations. We analyzed 183 Pi2 events simultaneously recorded at the 5 stations and discussed their possible generation mechanisms. The averaged dominant frequency of the H (horizontal) component is higher on the dawn side than that on the dusk side and shows a peak value in the post-midnight at around 03 LT, which confirms the LT dependence previously suggested from single station data (i.e., non-simultaneous observation). However, some of the events have no LT dependence. For the events which show the LT dependence at low-latitudes, we infer that the cavity resonance mode is a plausible generation mechanism, but we do not rule out the possibility of the plasmaspheric surface wave mode which has also been suggested. For the events having a common frequency between the eastern and western stations, we suggest the cavity resonance mode to be the mechanism. The averaged dominant frequency of the D component does not show any clear LT dependence, and only about 20% of Pi2s have identical frequency for both the H and D components, therefore we suggest that the H and D oscillations of Pi2s are generated from different mechanisms. We also found that the frequency of different parts of a Pi2 pulsation, i.e., the dominant frequency for leading part and trailing part of the pulsation, is different, and the frequency of the trailing part is lower than that of the leading part.