Low‐latitude Pi2 pulsations during intervals of quiet geomagnetic conditions (Kp≤1)
Low‐latitude Pi2 pulsations during intervals of quiet geomagnetic conditions (Kp≤1)
复制标题
安静地磁条件间隔期间的低纬度 Pi2 脉动（Kp≤1）
DOI：
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发表时间：
2013
期刊：
影响因子：
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通讯作者：
J. Hwang
中科院分区：
文献类型：
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作者：
H. Kwon;Khan;C. Jun;K. Takahashi;D. Lee;E. Lee;H. Jin;J. Seon;Y.‐D. Park;J. Hwang
据报道，Pi 2脉动可以在非常安静的地磁条件下激发（Kp=0）。然而，在这样一个近基态磁层中，很少有关于Pi 2脉动的全面报道。为了了解安静时间Pi 2脉动的特征，我们统计了当地时间18：00至06：00之间在韩国低纬度Bohyun（BOH，L = 1.35）站观测到的Pi 2事件。我们选择2008年进行分析，因为那一年的地磁活动异常低。当Kp≤1时，共识别出982起Pi 2事件。大约80%的Pi 2脉动的周期在110到300 s之间，这与传统的Pi 2周期（40到150 s）有很大的不同。比较Pi 2周期和太阳风条件，发现Pi 2周期随太阳风速度的增加而减小，这与特罗伊茨卡亚（1967）的结果一致。所观察到的波的性质进行了讨论，在等离子体层共振，这已被提出为Pi 2脉动的内磁层。我们还发现，Pi 2脉动发生准周期性的重复周期为1023 -38分钟。我们将讨论是什么决定了这样的重复时间的Pi 2脉动在安静的地磁条件下。
It has been reported that Pi2 pulsations can be excited under extremely quiet geomagnetic conditions (Kp=0). However, there have been few comprehensive reports of Pi2 pulsations in such a near ground state magnetosphere. To understand the characteristics of quiet‐time Pi2 pulsations, we statistically examined Pi2 events observed on the nightside between 1800 and 0600 local time at the low‐latitude Bohyun (BOH, L = 1.35) station in South Korea. We chose year 2008 for analysis because geomagnetic activity was unusually low in that year. A total of 982 Pi2 events were identified when Kp≤1. About 80% of the Pi2 pulsations had a period between 110 and 300 s, which significantly differs from the conventional Pi2 period from 40 to 150 s. Comparing Pi2 periods and solar wind conditions, we found that Pi2 periods decrease with increasing solar wind speed, consistent with the result of Troitskaya (1967). The observed wave properties are discussed in terms of plasmaspheric resonance, which has been proposed for Pi2 pulsations in the inner magnetosphere. We also found that Pi2 pulsations occur quasi‐periodically with a repetition period of ∼23–38 min. We will discuss what determines such a recurrence time of Pi2 pulsations under quiet geomagnetic conditions.