Transmission of an ICME Sheath Into the Earth's Magnetosheath and the Occurrence of Traveling Foreshocks
Transmission of an ICME Sheath Into the Earth's Magnetosheath and the Occurrence of Traveling Foreshocks
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DOI：
10.1029/2021ja029896
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发表时间：
2021-12
期刊：
影响因子：
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通讯作者：
M. Ala‐Lahti;A. Dimmock;T. Pulkkinen;S. Good;E. Yordanova;L. Turc;E. Kilpua
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文献类型：
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作者：
M. Ala‐Lahti;A. Dimmock;T. Pulkkinen;S. Good;E. Yordanova;L. Turc;E. Kilpua
通过研究2005年5月15日ICME鞘通道期间弓激波上游和下游的原位磁场测量，研究了由行星际日冕物质抛射驱动的鞘区到地球磁鞘的传输。我们观察到三个不同的时间间隔，在直接上游地区，包括一个向南的磁场分量，是旅行前震。这些行进的前震是在准平行弓形激波中观察到的，弓形激波承载着超低频的回流离子和磁波动。构成上游移动前震的间隔在传输到地球磁鞘后幸存下来，在那里它们的磁场，特别是向南的分量，被显着放大。我们的研究结果进一步表明，嵌入在ICME鞘层的磁场波动，如果它们的频率低于0.01赫兹，可以生存的传输。虽然其中一个确定的间隔是连贯的，延伸穿过ICME鞘并且是长寿命的，但预测可能从L1观测的上游传输到地球磁鞘的ICME鞘磁场具有模糊性。这可能是由于ICME鞘场在纵向方向上的强空间可变性，或者可替代地，由于ICME鞘场基本上在等离子体从L1传播到弓形激波所需的短时间内发展。这项研究表明，复杂的相互作用ICME鞘与地球的磁层时，通过地球。
The transmission of a sheath region driven by an interplanetary coronal mass ejection into the Earth's magnetosheath is studied by investigating in situ magnetic field measurements upstream and downstream of the bow shock during an ICME sheath passage on 15 May 2005. We observe three distinct intervals in the immediate upstream region that included a southward magnetic field component and are traveling foreshocks. These traveling foreshocks were observed in the quasi‐parallel bow shock that hosted backstreaming ions and magnetic fluctuations at ultralow frequencies. The intervals constituting traveling foreshocks in the upstream survive transmission to the Earth's magnetosheath, where their magnetic field, and particularly the southward component, was significantly amplified. Our results further suggest that the magnetic field fluctuations embedded in an ICME sheath may survive the transmission if their frequency is below ∼0.01 Hz. Although one of the identified intervals was coherent, extending across the ICME sheath and being long‐lived, predicting ICME sheath magnetic fields that may transmit to the Earth's magnetosheath from the upstream at L1 observations has ambiguity. This can result from the strong spatial variability of the ICME sheath fields in the longitudinal direction, or alternatively from the ICME sheath fields developing substantially within the short time it takes the plasma to propagate from L1 to the bow shock. This study demonstrates the complex interplay ICME sheaths have with the Earth's magnetosphere when passing by the planet.