Identification of substorm onset location and preonset sequence using Reimei, THEMIS GBO, PFISR, and Geotail
Identification of substorm onset location and preonset sequence using Reimei, THEMIS GBO, PFISR, and Geotail
复制标题
DOI：
10.1029/2010ja015520
复制
发表时间：
2010-12
影响因子：
--
通讯作者：
S. Zou;M. Moldwin;L. Lyons;Y. Nishimura;M. Hirahara;T. Sakanoi;K. Asamura;M. Nicolls;Y. Miyashita;S. Mende;C. Heinselman
中科院分区：
文献类型：
--
作者：
S. Zou;M. Moldwin;L. Lyons;Y. Nishimura;M. Hirahara;T. Sakanoi;K. Asamura;M. Nicolls;Y. Miyashita;S. Mende;C. Heinselman
我们介绍了2007年10月12日一次孤立亚暴的最先进的多仪器观测结果。Reimei， THEMIS ASI和PFISR同时观测到极光破裂。Geotail的脚印也在残骸附近。这些观测可以从大尺度和小尺度的极光形态、粒子降水和电离层对流等方面对破裂位置进行详细的研究，这是以前没有实现的。它还允许详细识别导致分手的顺序。我们报告了第一张星载高空间和时间分辨率的图像，其中部分是由Reimei拍摄的分裂弧和波状极光增强。观察结果表明，发病前约10分钟开始突然发生血浆薄层变薄。在破裂前约3分钟和约1分钟，在最靠近赤道的弧线处观察到两次波状极光增强。这些增强可能是由于一些近地不稳定性，比如气球不稳定性。与通常的亚暴序列不同，这个最靠近赤道的弧并没有发展成分裂弧，而是保持了几乎稳定的状态，直到爆发后被从高纬度向赤道方向的极光扩张所吞没。波状极光增强与三个细小的倒V弧有关，并嵌入在高能离子沉淀中。在这种增强之后，在高纬度恰好靠近等离子体薄片边界层（PSBL）的地方形成了一个弧，很可能是一个极向边界增强。这条弧随后向西南延伸，形成了位于波浪状构造的极地的破碎弧。假设离子沉降的纵向均匀性大于1°，则该破裂弧位于高能离子沉降的正极方向没有离子沉降的区域。这些观测结果表明，与PSBL附近的弧相关的低熵流通道可能存在，这可能与导致极光破裂的近地等离子体片的不稳定性有关。
[1] We present state-of-the-art multiple instrument observations of an isolated substorm on October 12, 2007. The auroral breakup was observed simultaneously by Reimei, THEMIS ASI, and PFISR. The footprint of Geotail was also near the breakup. These observations allow for detailed study of the breakup location in terms of large- and small-scale auroral morphology, particle precipitation, and ionospheric convection, which has not previously been achieved. It also allows for detailed identification of the sequence leading to the breakup. We report the first spaceborne high spatial and temporal resolution images of part of a breakup arc and a wave-like auroral enhancement captured by Reimei. Observations suggest a sudden plasma sheet thinning initiated ∼10 min before the onset. Wave-like auroral enhancements were observed twice at the most equatorward arc ∼3 min and ∼1 min before the breakup. These enhancements are likely due to some near-Earth instability, such as ballooning instability. Unlike the usual substorm sequence, this most equatorward arc did not develop into the breakup arc but remained almost stable until being engulfed by the auroral equatorward expansion from higher latitude after onset. The wave-like auroral enhancement was associated with three fine inverted V arcs and embedded within energetic ion precipitation. Following this enhancement, an arc, likely a poleward boundary intensification, formed at higher latitude just adjacent to the plasma sheet boundary layer (PSBL). This arc then extended southwestward and led to the breakup arc, which was located poleward of the wavy structures. Assuming longitudinal homogeneity of ion precipitation over 1°, this breakup arc was located in a region without ion precipitation just poleward of the energetic ion precipitation. These observations suggest the possible existence of a low-entropy flow channel associated with the arc adjacent to the PSBL, which might be associated with instability in the near-Earth plasma sheet responsible for the auroral breakup.