Successive substorm expansions during a period of prolonged northward interplanetary magnetic field
Successive substorm expansions during a period of prolonged northward interplanetary magnetic field
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DOI：
10.1029/2011ja016719
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发表时间：
2011-09
影响因子：
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通讯作者：
Y. Miyashita;Y. Kamide;K. Liou;Chin-Chun Wu;A. Ieda;N. Nishitani;S. Machida;Y. Saito;T. Mukai
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文献类型：
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作者：
Y. Miyashita;Y. Kamide;K. Liou;Chin-Chun Wu;A. Ieda;N. Nishitani;S. Machida;Y. Saito;T. Mukai
[1]我们已经研究了连续的亚暴扩张，尽管发生了一段时间的长期向北行星际磁场（IMF）。在北上的IMF持续了近2019小时后，1998年1月19日，在接下来的6小时间隔内，又出现了11个非常弱到中等强度的亚暴扩张，彼此之间相隔几十分钟。大部分亚暴的扩张并没有伴随着太阳风和IMF的显著变化。至于在向南的IMF条件下发生的典型亚暴，航天器和地面仪器观测到极光分裂和向西极光电喷流的增强以及电离层中的大规模对流，以及与亚暴扩张开始有关的磁尾中的等离子体团和双极化。这些签名表明，亚暴扩展的发病机制是相同的典型亚暴，即使在长期向北IMF的条件。我们认为，大的IMF的磁流影响大规模的对流和能量积累的磁尾和增强的对流，由于大的IMF的磁流效应和亚暴膨胀可能是一个重要的因素，促进后续的亚暴膨胀发作。
[1] We have studied successive substorm expansions that occurred in spite of a period of prolonged northward interplanetary magnetic field (IMF). After the northward IMF persisted for almost ∼19 h, a series of 11 very weak to moderate substorm expansions occurred during the following 6-h interval of northward IMF on 19 January 1998, separated from each other by a few tens of minutes. Most of these substorm expansions did not accompany significant changes of the solar wind and the IMF. As for typical substorms that occur under southward IMF conditions, spacecraft and ground-based instruments observed auroral breakups and enhancements of the westward auroral electrojet and large-scale convection in the ionosphere, together with plasmoids and dipolarizations in the magnetotail, in association with the substorm expansion onsets. These signatures suggest that the mechanism of substorm expansion onsets is the same as for typical substorms, even under prolonged northward IMF conditions. We suggest that the large IMF ∣By∣ affects large-scale convection and energy accumulation in the magnetotail and that the enhanced convection due to the large IMF ∣By∣ effect and substorm expansions can be an important factor for the promotion of succeeding substorm expansion onsets.