A Statistical Study of Pi2 Pulsations Observed in the Upper Ionosphere Using Swarm Magnetic Field Data
A Statistical Study of Pi2 Pulsations Observed in the Upper Ionosphere Using Swarm Magnetic Field Data
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利用群磁场数据对电离层上部观测到的 Pi2 脉动进行统计研究
DOI：
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发表时间：
2020
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：
Jae‐Hee Park;Khan‐Hyuk Kim;H. Kwon;G. Jee;J. Hwang
利用2014年1月至2015年6月由Swarm A航天器在低地球轨道和低纬度Bohyun地面站（BOH， L=1.3）采集的磁场数据，研究了在电离层上层观测到的Pi2脉动特性。从A群位于夜侧（磁地方时(MLT) = 1800-0600小时）和BOH站接近午夜（MLT = 2100-0300小时）的时间间隔来看，我们在BOH数据的水平H分量中确定了621个Pi2事件。对于每个事件，我们检查了地面水平H分量与a群的Bx（径向）、By（方角）或Bz（压缩）分量之间的相干性。在621个事件中，Bx−H高相干性（>.7）事件为~ 6%，By−H高相干性事件为~ 2%，Bz−H高相干性事件为~ 25%。地面卫星高相干事件发生在航天器位于磁纬- 50°和50°之间时。利用地面卫星高相干事件，我们统计检验了电离层Pi2脉动的相对振幅和相位的纬向结构，发现它们的纬向变化与等离子体共振模型所期望的南北模态结构一致。我们的统计结果表明，电离层Pi2脉动的来源是等离子体共振。
The properties of Pi2 pulsations observed in the upper ionosphere are studied using magnetic field data acquired by the Swarm A spacecraft in low Earth orbit and at the low‐latitude Bohyun ground station (BOH, L=1.3) for January 2014 to June 2015. From time intervals when Swarm A was on the nightside (magnetic local time (MLT) = 1800–0600 hr) and the BOH station was near midnight (MLT = 2100–0300 hr), we identified 621 Pi2 events in the horizontal H component of the BOH data. For each event we examined the coherence between the horizontal H component on the ground and the Bx (radial), By (azimuthal), or Bz (compressional) components at Swarm A. Out of 621 events, the Bx−H high‐coherence (> 0.7) events are ∼6%, the By−H high‐coherence events are ∼2%, and the Bz−H high‐coherence events are ∼25%. The ground satellite high‐coherence events occurred when the spacecraft was located at magnetic latitudes between −50° and 50°. Using the ground satellite high‐coherence events, we statistically examined the latitudinal structure of the relative amplitude and phase of the ionospheric Pi2 pulsations and found that their latitudinal variations is consistent with the north‐south mode structure expected from the plasmaspheric resonance model. Our statistical results indicate that the source of ionospheric Pi2 pulsations is the plasmaspheric resonance.