Conjugate Ground‐Spacecraft Observations of VLF Chorus Elements
Conjugate Ground‐Spacecraft Observations of VLF Chorus Elements
复制标题
甚低频合唱元素的地面航天器共轭观测
DOI：
10.1002/2017gl076139
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发表时间：
2017
影响因子：
5.2
通讯作者：
E. Titova
中科院分区：
文献类型：
--
作者：
A. Demekhov;J. Manninen;O. Santolík;E. Titova
我们介绍了在芬兰北部的Kannuslehto地面站和Van Allen探测器A上同时观测VLF合唱元素的结果。对数据的目测检查和相关分析表明，一个序列中相互紧随的几个(至少12个)合唱元素一一对应。由Van Allen探测器A上的电磁场仪器套件和综合科学仪器测量的电磁场计算的坡印亭通量表明，波的传播方向与地磁场成小角度相反，即从北半球到南半球。该航天器位于L≃4.1号，地磁纬度−12.4∘，靠近等离子体顶层，处于密度增加约30%的局域密度不均匀内部，横向尺寸约600公里。地面探测到的波与航天器上探测到的波之间的时延约为1.3%S，地面探测领先于航天器探测。对于等离子体密度沿场线分布的真实轮廓，测量的时间延迟与准平行哨声模波的行进时间一致。结果表明，合唱离散元素可以在从产生区到地面的跳跃过程中保持其光谱形状，然后从电离层反射并返回近赤道区。
We present results of simultaneous observations of VLF chorus elements at the ground‐based station Kannuslehto in Northern Finland and on board Van Allen Probe A. Visual inspection and correlation analysis of the data reveal one‐to‐one correspondence of several (at least 12) chorus elements following each other in a sequence. Poynting flux calculated from electromagnetic fields measured by the Electric and Magnetic Field Instrument Suite and Integrated Science instrument on board Van Allen Probe A shows that the waves propagate at small angles to the geomagnetic field and oppositely to its direction, that is, from northern to southern geographic hemisphere. The spacecraft was located at L≃4.1 at a geomagnetic latitude of −12.4∘ close to the plasmapause and inside a localized density inhomogeneity with about 30% density increase and a transverse size of about 600 km. The time delay between the waves detected on the ground and on the spacecraft is about 1.3 s, with ground‐based detection leading spacecraft detection. The measured time delay is consistent with the wave travel time of quasi‐parallel whistler‐mode waves for a realistic profile of the plasma density distribution along the field line. The results suggest that chorus discrete elements can preserve their spectral shape during a hop from the generation region to the ground followed by reflection from the ionosphere and return to the near‐equatorial region.