Propagation of ULF waves from the upstream region to the midnight sector of the inner magnetosphere
Propagation of ULF waves from the upstream region to the midnight sector of the inner magnetosphere
复制标题
ULF波从上游区域到内磁层午夜区域的传播
DOI：
10.1002/2016ja022958
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发表时间：
2016
期刊：
影响因子：
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通讯作者：
A. Yoshikawa
中科院分区：
文献类型：
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作者：
Kazue Takahashi;M. Hartinger;D. Malaspina;Charles W. Smith;K. Koga;H. Singer;D. Frühauff;D. Baishev;A. Moiseev;A. Yoshikawa
离子前震中产生的超低频（ULF）波是在日侧磁层中观察到的 Pc3-Pc4 波（7-100 mHz）的众所周知的来源。我们使用多个航天器于 2013 年 4 月 10 日获取的数据来证明上游起源的 ULF 波可以传播到内磁层的午夜区域。在选定日期的 1130–1730 UT，两艘范艾伦探测器航天器和对地静止 ETS-VIII 卫星在午夜区域的 L ∼ 4 和 L ∼ 7 之间以及接近中午的其他航天器上检测到了 20 到 40 mHz 的压缩磁场振荡。振荡的上游起源是根据与理论模型相匹配的波频率、全局相干幅度调制和黄昏传播得出的结论，该传播与在观测到的行星际磁场下通过黎明侧翼的上游波能量的预期进入一致。根据~300 km/s 的传播速度以及电场和磁场扰动之间的关系，这些振荡归因于磁流体动力快模波。方位角波数的大小估计为~30。没有证据表明振荡在午夜区域传播到地面。
Ultralow frequency (ULF) waves generated in the ion foreshock are a well‐known source of Pc3‐Pc4 waves (7–100 mHz) observed in the dayside magnetosphere. We use data acquired on 10 April 2013 by multiple spacecraft to demonstrate that ULF waves of upstream origin can propagate to the midnight sector of the inner magnetosphere. At 1130–1730 UT on the selected day, the two Van Allen Probes spacecraft and the geostationary ETS‐VIII satellite detected compressional 20 to 40 mHz magnetic field oscillations between L ∼ 4 and L ∼ 7 in the midnight sector, along with other spacecraft located closer to noon. Upstream origin of the oscillations is concluded from the wave frequency that matches a theoretical model, globally coherent amplitude modulation, and duskward propagation that is consistent with expected entry of the upstream wave energy through the dawnside flank under the observed interplanetary magnetic field. The oscillations are attributed to magnetohydrodynamic fast‐mode waves based on their propagation velocity of ∼300 km/s and the relationship between the electric and magnetic field perturbations. The magnitude of the azimuthal wave number is estimated to be ∼30. There is no evidence that the oscillations propagated to the ground in the midnight sector.