A case study in support of closure of bow shock current through the ionosphere utilizing multi-point observations and simulation
A case study in support of closure of bow shock current through the ionosphere utilizing multi-point observations and simulation
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DOI：
10.3389/fspas.2023.1098388
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发表时间：
2021-03
期刊：
影响因子：
--
通讯作者：
P. Dredger;R. Lopez;M. Hamrin
中科院分区：
文献类型：
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作者：
P. Dredger;R. Lopez;M. Hamrin
在地球磁层前面的弓形激波上，由于行星际磁场在激波上的旋度而产生了电流。这一洋流的结束仍不确定；目前尚不清楚弓形激波电流是否在磁层顶与查普曼-费拉罗电流系统关闭，沿着磁场线进入电离层，通过磁鞘，或两者的某种组合。本文介绍了磁层多尺度（MMS）、AMPERE和国防气象卫星计划（DMSP）在强B y、弱负B z和极小B x期间的同步观测结果。这种IMF方向应该导致弓形激波电流在激波上主要由南向北流动。AMPERE显示了1区和2区伯克兰电流向极地方向流入北极帽并从南部流出，这是弓形激波电流沿着开放磁场线闭合的正确极性。南方国防气象卫星计划F18立交桥证实，这一洋流在对流逆转边界的两极方向。此外，我们利用MHD模拟研究了上述太阳风条件下弓形激波电流的闭合。我们将由于IMF B y分量而模拟的弓形激波电流的大小与模拟的高纬度电流的大小进行了比较，该高纬度电流对应于在AMPERE和国防气象卫星计划中观测到的实际电流。在模拟中，1区电流向极方向的电流在北部电离层约为弓形激波I z的37%，在南部约为60%。我们的结论是，证据指向至少部分关闭弓形激波电流通过电离层。
On the bow shock in front of Earth’s magnetosphere flows a current due to the curl of the interplanetary magnetic field across the shock. The closure of this current remains uncertain; it is unknown whether the bow shock current closes with the Chapman-Ferraro current system on the magnetopause, along magnetic field lines into the ionosphere, through the magnetosheath, or some combination thereof. We present simultaneous observations from Magnetosphere Multiscale (MMS), AMPERE, and Defense Meteorological Satellite Program (DMSP) during a period of strong B y , weakly negative B z , and very small B x . This IMF orientation should lead to a bow shock current flowing mostly south to north on the shock. AMPERE shows a current poleward of the Region 1 and Region 2 Birkeland currents flowing into the northern polar cap and out of the south, the correct polarity for bow shock current to be closing along open field lines. A southern Defense Meteorological Satellite Program F18 flyover confirms that this current is poleward of the convection reversal boundary. Additionally, we investigate the bow shock current closure for the above-mentioned solar wind conditions using an MHD simulation of the event. We compare the magnitude of the modeled bow shock current due to the IMF B y component to the magnitude of the modeled high-latitude current that corresponds to the real current observed in AMPERE and by Defense Meteorological Satellite Program. In the simulation, the current poleward of the Region 1 currents is about 37% as large as the bow shock I z in the northern ionosphere and 60% in the south. We conclude that the evidence points to at least a partial closure of the bow shock current through the ionosphere.