Investigating the Spatiotemporal Development of Substorm Expansion Phase Aurora: Successive Onsets or Poleward Boundary Intensifications?

IF 2.6 2区 地球科学 Q2 ASTRONOMY & ASTROPHYSICS
Sneha Yadav, Larry R. Lyons, Yukitoshi Nishimura, Jiang Liu, Sheng Tian, Ying Zou, Eric F. Donovan
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Abstract

Following the auroral substorm onset, the active aurora undergoes expansion, which can vary in spatial and temporal extent. The spatiotemporal development of the expansion phase active aurora is controlled by new auroral intensifications that often follow the initial onset. Using seven examples, we investigate the nature of these new auroral intensifications and address a question: are they new auroral onsets, that is, “successive onsets” or poleward-boundary intensifications (PBIs) and ensuing auroral streamers? We observed events that included both types of auroral features—successive onsets and PBIs—and their combinations. For multiple-onset substorms, successive onsets may occur eastward, westward, and poleward of the initial onset, resulting in a diverse range of expansion phase spatial extent and durations. Single-onset substorms show only one auroral onset, but their spatiotemporal development can resemble that of multiple-onset substorms. However, the additional activations are mainly PBIs and subsequent streamers. In some cases, PBIs undergo explosion, leading to a rapid poleward and azimuthal expansion of the aurora, resembling the auroral substorm onset. A prolonged sequence of PBIs and its longitudinal extension can contribute significantly to the spatiotemporal development of substorms expansion phase. Results suggest that post-onset flow channels drive the spatiotemporal development of the substorm expansion phase by (a) triggering successive onsets and (b) inducing bursts of PBIs and their prolonged sequence. We speculate that post-onset flow channels likely originate from the polar cap, but more evaluation is required. Our findings highlight the significance of examining imager data before solely relying on magnetometers to identify substorm onsets.

亚暴膨胀期极光的时空发展:连续发作还是向极地边界增强?
在极光亚暴发生后,活跃极光会发生扩展,这种扩展在时空上是不同的。扩展期活动极光的时空发展受新的极光强化控制,这些强化通常是在初始极光开始后出现的。通过七个例子,我们研究了这些新的极光强化的性质,并提出了一个问题:它们是新的极光开始,即“连续开始”还是极地边界增强(pbi)和随后的极光流光?我们观察到的事件包括两种类型的极光特征-连续发作和pbi -及其组合。对于多次发作的亚暴,连续发作可能发生在初始发作的东部、西部和极地,导致扩展阶段空间范围和持续时间的不同范围。单次亚暴只有一次极光爆发,但其时空发展与多次亚暴相似。然而,额外的激活主要是pbi和随后的拖缆。在某些情况下,pbi发生爆炸,导致极光迅速向极地和方位角扩展,类似于极光亚暴的开始。pbi序列的延长及其纵向扩展对亚暴扩展期的时空发展有重要影响。研究结果表明,亚暴扩展期的时空发展主要是通过(a)触发连续的爆发和(b)诱导pbi的爆发及其延长的序列来驱动的。我们推测,开始后的水流通道可能起源于极帽,但需要更多的评估。我们的发现强调了在仅仅依靠磁力计来识别亚暴爆发之前检查成像仪数据的重要性。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Journal of Geophysical Research: Space Physics
Journal of Geophysical Research: Space Physics Earth and Planetary Sciences-Geophysics
CiteScore
5.30
自引率
35.70%
发文量
570
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