Dynamics of the substorm expansive phase
Dynamics of the substorm expansive phase
复制标题
亚暴扩张阶段的动力学
DOI：
10.1029/2000ja000292
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发表时间：
2001
影响因子：
--
通讯作者：
G. Rostoker
中科院分区：
文献类型：
--
作者：
E. Friedrich;J. Samson;I. Voronkov;G. Rostoker
来自加拿大开放方案统一研究极光网络地面阵列的子午线扫描光度计和磁力计数据已被用于研究亚暴扩张阶段的动态。MSP 630.0，557.7，和486.1 nm的排放量为8个孤立的事件的相对纬向运动进行了研究。数据显示，扩张阶段包括三个阶段：爆发（数十秒）开始;几分钟量级的557.7 nm发射的快速向极运动;以及一段较慢（数十分钟）的向极移动630.0 nm发射。我们解释的快速向极运动的557.7 nm的数据在一个区域的不稳定性，迅速扩大了磁尾，可能加速等离子体片电子，因为它的收益。所有的事件表明，瓣通量重联发生后，近地发病，典型的时间延迟1和5分钟之间。非常短的时间间隔之间的近地发病和瓣通量重联的开始提出了一个严重的观测约束任何亚暴模型，试图解释亚暴膨胀阶段。CANOPUS丘吉尔线的磁强计数据已被用来研究亚暴的增长和早期扩张阶段的亚暴电射流的动力学。这些电射流的边界在生长和膨胀阶段密切遵循MSP数据的运动。在扩张阶段开始的瞬间，增长阶段的电射流（如沿着丘吉尔子午线观察到的）消失，被与当前楔形相关的亚暴向西电射流所取代。亚暴向西电射流的赤道边界嵌入质子极光发射中，并出现在扩张相开始时，向赤道方向的增长阶段电射流的0.2 °，进一步显示了扩张相开始的近地接近。没有迹象表明重新连接封闭的磁力线之前，膨胀阶段发病观察到的磁力计或光度计的数据。
Meridian-scanning photometer (MSP) and magnetometer data from the Canadian Auroral Network for the OPEN Program Unified Study (CANOPUS) ground-based array have been used to study the dynamics of the substorm expansive phase. The relative latitudinal motions of the MSP 630.0, 557.7, and 486.1 nm emissions for eight isolated events have been studied. The data show the expansive phase to comprise three stages: an explosive (tens of seconds) onset; rapid poleward motion of 557.7 nm emissions of the order of a few minutes; and a period of slower (tens of minutes) poleward moving 630.0 nm emissions. We interpret the rapid poleward motion of the 557.7 nm data in terms of a region of instability, expanding rapidly down the magnetotail, possibly accelerating plasma sheet electrons as it proceeds. All events show that lobe flux reconnection occurs after near-Earth onset, with typical time delays between 1 and 5 min. The extremely short time interval between near-Earth onset and the beginning of lobe flux reconnection presents a severe observational constraint on any substorm model which attempts to explain the substorm expansive phase. Magnetometer data from the CANOPUS Churchill line have been used to study the dynamics of the substorm electrojets during the growth and early expansive phases of the substorm. The borders of these electrojets closely follow the motion of the MSP data during the growth and expansive phases. At the instant of expansive phase onset the growth phase electrojets (as observed along the Churchill meridian line) disappear, being replaced by the substorm westward electrojet associated with the current wedge. The equatorward border of the substorm westward electrojet is embedded within the proton aurora emissions and appears at expansive phase onset ∼2° equatorward of the growth phase electrojets, further showing the near-Earth proximity of expansive phase onset. No indication of reconnection on closed field lines prior to expansive phase onset was observed in either the magnetometer or the photometer data.