Poleward Moving Auroral Arcs and Pc5 Oscillations
Poleward Moving Auroral Arcs and Pc5 Oscillations
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DOI：
10.1029/2022ja030362
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发表时间：
2022-06
期刊：
影响因子：
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通讯作者：
T. Sakurai;A. Wright;K. Takahashi;T. Elsden;Y. Ebihara;N. Sato;A. Kadokura;Y. Tanaka;T. Hori
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文献类型：
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作者：
T. Sakurai;A. Wright;K. Takahashi;T. Elsden;Y. Ebihara;N. Sato;A. Kadokura;Y. Tanaka;T. Hori
我们提出了一个例子，极向移动极光弧（PMAA）和Pc 5振荡观察到的亚暴期间的事件和大尺度相互作用的时间历史（THEMIS）地面观测站吉勒姆之间的一一对应关系。PMAA由四个连续的增强（命名为PMAA 1，PMAA 2，PMAA 3和PMAA 4）组成，周期为3 - 4min，位于极光椭圆的磁纬度68 °至70 °，并与磁场Pc 5振荡的H分量相干变化。PMAA1和PMAA2在磁纬<$69 °出现明显，而PMAA2和PMAA3在磁纬<$68 °出现较暗。PMAA 1和PMAA 2表现出场线共振的特征，其最大光度分别位于磁纬<$69.5 °和<$69.4 °。地面Pc5振荡与THEMIS-D、-E和-A卫星在外磁层104 MLT观测到的环形模式Pc5振荡同时发生。THEMIS的磁场和电场振荡与PMAA同步。THEMIS Pc 5振荡的磁能估计使用阻尼环形振荡的数值模型，并与沉淀电子的动能与由环形振荡携带的场对准电流相关联。结果表明，Pc5磁场能量远大于动能，说明磁场能量对电离层极光辐射的产生起着重要作用。我们还进行了PMAAs和环形模式Pc 5振荡之间的关系的模拟。模拟解释了观测到的PMAAs的空间和时间结构。
We present an example of one‐to‐one correspondence between poleward moving auroral arcs (PMAAs) and Pc5 oscillations observed at the Time History of Events and Macroscale Interactions during Substorms (THEMIS) Ground Based Observatory station Gillam. The PMAAs consisted of four successive intensifications (named PMAA1, PMAA2, PMAA3 and PMAA4) with a period of 3∼4 min over the magnetic latitudes from 68° to 70° in the auroral oval and varied coherently with the H‐component of magnetic field Pc5 oscillations. PMAA1 and PMAA2 appeared clearly at the magnetic latitude ∼69°, and the following two PMAAs, which were dimmer, appeared at the magnetic latitude ∼68°. PMAA1 and PMAA2 exhibited features of field‐line resonances with the maximum luminosity at the magnetic latitude ∼69.5° and ∼69.4°, respectively. The ground Pc5 oscillations were concurrent with toroidal mode Pc5 oscillation observed at the THEMIS‐D, ‐E, and ‐A satellites at ∼4 MLT in the outer magnetosphere. The magnetic and electric field oscillations at THEMIS were synchronized with the PMAAs. The magnetic energy of the THEMIS Pc5 oscillations is estimated using a numerical model of damped toroidal oscillations and compared with the kinetic energy of precipitating electrons associated with the field aligned current carried by the toroidal oscillations. The result reveals that the Pc5 magnetic energy is much larger than the kinetic energy, implying the magnetic energy is important for producing auroral emissions in the ionosphere. We also perform a simulation of the relationship between PMAAs and toroidal mode Pc5 oscillations. The simulation explains the observed spatial and temporal structures of the PMAAs.