On the relationships between double‐onset substorm, pseudobreakup, and IMF variation: The 4 September 1999 event
On the relationships between double‐onset substorm, pseudobreakup, and IMF variation: The 4 September 1999 event
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DOI：
10.1029/2004ja010778
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发表时间：
2005-07
影响因子：
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通讯作者：
Ching-Chang Cheng;C. Russell;G. Reeves;M. Connors;M. Moldwin
中科院分区：
文献类型：
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作者：
Ching-Chang Cheng;C. Russell;G. Reeves;M. Connors;M. Moldwin
[1]利用1999年9月4日世界协调时0200-0600之间从空间到地面的磁、极光和粒子观测资料，研究了双发亚暴、假破裂和IMF变化之间的关系。在感兴趣的时间内，地面上有五次连续的Pi 2脉冲爆发。地面Pi 2s的起始时间映射到上游区域多个卫星观测中传播到地球的IMF结构中的相同变化序列。极光和高能粒子的数据与IMF的观测结果的比较表明，一个序列的两个双发病亚暴干预的pseudoblutation出现在两个不同的周期向南IMF随后由一个向北的间隔。对于第一个亚暴，第一次爆发发生在IMF转向南行约90 min后的By震级下降时，第二次爆发发生在IMF转向北行并伴随By震级增加后。当IMF转向南行时，出现了伪破裂，By震级略有减小。对于第二个亚风暴，第一次爆发开始时，IMF保持向南，并具有稳定的By级，第二次爆发发生在IMF变得强烈北上，而By级反而减少之后。这些现象可以用两个中性点模型来解释。当IMF转向南方时，第一次发作发生。在近地中性点的重联首先开始于等离子体片内的闭合场线上，第二次发生在IMF转向北时，在远处中性点的重联停止，在近地中性点的重联可能达到尾瓣的开放通量。此外，By量级的降低可能有助于减少磁尾对流并释放所有累积的通量，以便在IMF向北转向后开始爆发。如果IMF继续向南移动，则由于By的减少而导致磁尾对流的减少将导致伪分裂。相反，B y的增加将增加磁尾对流和减弱后，IMF转向北磁层亚暴。因此，对于双发亚暴和伪破裂的发生，不仅第一次发作自发地开始在稳定的南向IMF和第二次发作后出现的IMF转向北，但由变化也影响磁尾对流，这可能会引发（或减弱）亚暴相关的激活，而IMF转向南（或北）。
[1] The relationships between double-onset substorm, pseudobreakup, and IMF variation were investigated with magnetic, auroral, and particle observations from space to the ground during 0200-0600 UT on 4 September 1999. There were five consecutive bursts of Pi2 pulsations on the ground during the time of interest. The onset time of ground Pi2s maps to the same variation sequence in the IMF structure seen propagating to the Earth in multiple satellite observations in the upstream region. The comparison of auroral and energetic particle data with IMF observations shows that a sequence of two double-onset substorms intervened by a pseudobreakup appears in two distinct cycles of southward IMF followed by a northward interval. For the first substorm, the first onset begins when the By magnitude declines after the IMF turns southward for about 90 min, and the second onset occurs after northward turning of the IMF accompanied by an increasing By magnitude. The pseudobreakup appears while the IMF turns southward and the By magnitude slightly decreases. For the second substorm, the first onset commences while the IMF remains southward with a steady By magnitude, and the second onset occurs after the IMF becomes strongly northward and the By magnitude decreases instead. These observations can be explained with the two-neutral-point model. The first onset occurs when the IMF turns southward. Reconnection at the near-Earth neutral point first begins on closed field lines within the plasma sheet, and the second onset occurs when the IMF turns northward and reconnection at the distant neutral point ceases and reconnection at the near-Earth neutral point may reach the open flux of the tail lobes. In addition, a decrease in the By magnitude may help reduce magnetotail convection and release all the built-up flux to allow the onset to commence after northward turning of the IMF. If the IMF remains southward, the reduction of magnetotail convection due to a decreasing By would lead to a pseudobreakup instead. In contrast, an increasing B y magnitude would increase magnetotail convection and weaken magnetospheric substorm after the IMF turns northward. Consequently, for the occurrence of double-onset substorms and pseudobreakups, not only the first onset begins spontaneously during steady southward IMF and the second onset appears after northward turning of the IMF but the By change also affects magnetotail convection which may evoke (or abate) the substorm-related activation while the IMF turns southward (or northward).