A statistical study of longitudinal extent of Pc1 pulsations using seven PWING ground stations at subauroral latitudes
A statistical study of longitudinal extent of Pc1 pulsations using seven PWING ground stations at subauroral latitudes
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使用亚极光纬度的七个 PWING 地面站对 Pc1 脉动纵向范围进行统计研究
DOI：
10.1029/2021ja029987
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发表时间：
2023
影响因子：
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通讯作者：
and T. Raita
中科院分区：
文献类型：
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作者：
Liu;J.;K. Shiokawa;S. Oyama;Y. Otsuka;C.-W. Jun;M. Nose;T. Nagatsuma;K. Sakaguchi;A. Kadokura;M. Ozaki;M. Connors;D. Baishev;N. Nishitani;A. Oinats.;V. Kurkin;and T. Raita
Pc 1地磁脉动对应于磁层中的电磁离子回旋（EMIC）波，并以0.2-5 Hz的频率在那里激发。Pc 1波在地面上的瞬时纵向范围尚未估计。在这项研究中，我们分析了2018年7月至2019年6月期间在极光下纬度60°磁纬的7个纵向分布的地面站观测到的Pc 1脉动。所有7个台站的Pc 1脉动每小时发生率在中午后的扇区有一个峰值（14%-39.6%），在午夜有一个局部最小值（4.1%-8.1%）。平均频率在午夜后最高（0.6-1.1 Hz），中午后最低（0.3-0.5 Hz）。总Pc 1发生相对于磁纬度的增加趋势进行了观察。在此基础上，我们得到了瞬时Pc 1经向范围的概率分布的峰值为φ 82.5°，半峰值为φ 114°，但这种概率分布受台站数目的限制而受到影响。我们还用人工随机Pc 1波对可能的纵向范围进行了模型计算。模式计算结果与观测结果的比较表明，70° ~ 86 °的纵向范围与概率分布的峰值（φ 82.5°）相当。叠加历元分析表明，在磁暴恢复阶段，Pc 1波的纵向幅度有增大的趋势。
Pc1 geomagnetic pulsations correspond to electromagnetic ion cyclotron (EMIC) waves in the magnetosphere and are excited there with frequencies of 0.2–5 Hz. The instantaneous longitudinal extent of Pc1 waves on the ground has not been estimated yet. In this study, we analyze the Pc1 pulsations observed at seven longitudinally‐distributed ground stations at subauroral latitudes at ∼60° magnetic latitude for 1 year from July 2018 to June 2019. The hourly occurrence rates of Pc1 pulsations at all 7 stations have a peak (14%–39.6%) in the post‐noon sector and a local minimum (4.1%–8.1%) at midnight. The average frequencies become highest (0.6–1.1 Hz) after midnight and lowest (0.3–0.5 Hz) after noon at all 7 stations. An increasing tendency of total Pc1 occurrence with respect to magnetic latitude was observed. Based on these observations, we obtained a peak of probability distribution of the instantaneous Pc1 longitudinal extent as ∼82.5° with a half maximum at ∼114°, though this probability distribution can be affected by the limitation of the number of the stations. We also made model calculations on the possible longitudinal extent using artificial random Pc1 waves with fixed extents. The comparison of the model results with the observation suggests longitudinal extent of 70°–86° comparable to the peak of probability distribution (∼82.5°). A superposed epoch analysis shows that the longitudinal extent of Pc1 waves tends to increase during recovery phase of geomagnetic storms.