Yao Zhonghua, Pu Z Y, Rae I J, Radioti A, Kubyshkina M V
1Laboratoire de Physique Atmosphérique et Planétaire, STAR institute, Université de Liège, Liège, Belgium.
2School of Earth and Space Sciences, Peking University, Beijing, China.
Geosci Lett. 2017;4(1):8. doi: 10.1186/s40562-017-0075-6. Epub 2017 Apr 11.
The time scales of reconnection outflow, substorm expansion, and development of instabilities in the terrestrial magnetosphere are comparable, i.e., from several to tens of minutes, and their existence is related. In this paper, we investigate the physical relations among those phenomena with measurements during a substorm event on January 29, 2008. We present conjugate measurements from ground-based high-temporal resolution all-sky imagers and in situ THEMIS measurements. An auroral streamer (north-south aligned thin auroral layer) was formed and propagated equatorward, which usually implies an earthward propagating plasma flow in the magnetotail. At the most equatorward part of the auroral streamer, a wave-like auroral band was formed aligning in the east-west direction. The wave-like auroral structure is usually explained as a consequence of instability development. Using AM03 model, we trace the auroral structure to magnetotail and estimate a wavelength of ~0.5 . The scale is comparable to the drift mode wavelength determined by the in situ measurements from THEMIS-A, whose footpoint is on the wave-like auroral arc. We also present similar wave-like aurora observations from Cassini ultraviolet imaging spectrograph at Saturn and from Hubble space telescope at Jupiter, suggesting that the wave-like aurora structure is likely a result of fundamental plasma dynamics in the solar system planetary magnetospheres.
地球磁层中重联流出、亚暴膨胀以及不稳定性发展的时间尺度是可比的，即从几分钟到几十分钟，并且它们的存在是相关的。在本文中，我们利用2008年1月29日一次亚暴事件期间的测量数据来研究这些现象之间的物理关系。我们展示了地面高时间分辨率全天空成像仪的共轭测量结果以及THEMIS的原位测量结果。一条极光带（南北向排列的薄极光层）形成并向赤道方向传播，这通常意味着磁尾中有一股向地球方向传播的等离子体流。在极光带最靠赤道的部分，形成了一条东西向排列的波状极光带。这种波状极光结构通常被解释为不稳定性发展的结果。利用AM03模型，我们将极光结构追溯到磁尾并估计其波长约为0.5 。这个尺度与由THEMIS - A的原位测量确定的漂移模波长相当，THEMIS - A的脚点位于波状极光弧上。我们还展示了来自土星的卡西尼紫外成像光谱仪和木星的哈勃太空望远镜的类似波状极光观测结果，这表明波状极光结构可能是太阳系行星磁层中基本等离子体动力学的结果。
