Propagation of Ultralow‐Frequency Waves from the Ion Foreshock into the Magnetosphere During the Passage of a Magnetic Cloud
Propagation of Ultralow‐Frequency Waves from the Ion Foreshock into the Magnetosphere During the Passage of a Magnetic Cloud
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在磁云通过期间从离子前震到磁层的超低频波的传播
DOI：
10.1029/2020ja028474
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发表时间：
2021
期刊：
影响因子：
--
通讯作者：
Motoba, Tetsuo
中科院分区：
文献类型：
--
作者：
Takahashi, Kazue;Turc, Lucile;Kilpua, Emilia;Takahashi, Naoko;Dimmock, Andrew;Kajdic, Primoz;Palmroth, Minna;Pfau‐Kempf, Yann;Soucek, Jan;Motoba, Tetsuo
我们研究了地球与太阳风中的磁云相遇时空间（离子前震、磁鞘和磁层）和白天磁力计站（L= 1.6-6.5）的超低频（ULF）波的特性，其特征是磁场强度大（~ 14 nT）和锥角小（~ 30°）。在前震中，波在理论预期的~ 90 m Hz被激发，但在其他频率也有振荡。在空间的其他位置也检测到90兆赫附近的振荡，但它们通常不是最主要的振荡。在地面上，所有台站连续检测到Pc2-Pc4近似频段（5 mHz - 120 mHz）的脉动，除了驻波alfvsamn三次谐波频率为该频率的台站外，h分量在90 mHz附近没有明显的频谱峰值。各台站基频环向波频率均在90兆赫以下。在d分量谱中，位于l < 3的站点在90 mHz附近出现一个小谱峰，功率在该频率以上突然下降。磁层纵波能在夜侧弱得多。混合- Vlasov模拟表明，前震ULF波具有较短的空间尺度长度，并且传输到磁层的波在正午之后被强烈衰减。
We have examined the properties of ultralow‐frequency (ULF) waves in space (the ion foreshock, magnetosheath, and magnetosphere) and at dayside magnetometer stations (L= 1.6–6.5) during Earth's encounter with a magnetic cloud in the solar wind, which is characterized by magnetic fields with large magnitudes (∼14 nT) and small cone angles (∼30°). In the foreshock, waves were excited at ∼90 m Hz as expected from theory, but there were oscillations at other frequencies as well. Oscillations near 90 mHz were detected at the other locations in space, but they were not in general the most dominant oscillations. On the ground, pulsations in the approximate Pc2–Pc4 band (5 mHz–120 mHz) were continuously detected at all stations, with no outstanding spectral peaks near 90 mHz in theHcomponent except at stations where the frequency of the third harmonic of standing Alfvén waves had this frequency. The fundamental toroidal wave frequency was below 90 mHz at all stations. In theDcomponent spectra, a minor spectral peak is found near 90 mHz at stations located atL< 3, and the power dropped abruptly above this frequency. Magnetospheric compressional wave power was much weaker on the nightside. A hybrid‐Vlasov simulation indicates that foreshock ULF waves have short spatial scale lengths and waves transmitted into the magnetosphere are strongly attenuated away from noon.
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DOI：
10.1002/2016ja022958
发表时间：
2016
期刊：
Journal of Geophysical Research: Space Physics
影响因子：
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影响因子：
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作者：
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发表时间：
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