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首页> 外文期刊>Journal of Geophysical Research, A. Space Physics: JGR >Substorm evolution of auroral structures
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Substorm evolution of auroral structures

机译：亚暴极光结构的演化

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Auroral arcs are often associated with magnetically quiet time and substorm growth phases. We have studied the evolution of auroral structures during global and local magnetic activity to investigate the occurrence rate of auroral arcs during different levels of magnetic activity. The ground-magnetic and auroral conditions are described by the magnetometer and auroral camera data from five Magnetometers - Ionospheric radars - All-sky cameras Large Experiment stations in Finnish and Swedish Lapland. We identified substorm growth, expansion, and recovery phases from the local electrojet index (IL) in 1996–2007 and analyzed the auroral structures during the different phases. Auroral structures were also analyzed during different global magnetic activity levels, as described by the planetary Kp index. The distribution of auroral structures for all substorm phases and Kp levels is of similar shape. About one third of all detected structures are auroral arcs. This suggests that auroral arcs occur in all conditions as the main element of the aurora. The most arc-dominated substorm phases occur in the premidnight sector, while the least arc-dominated substorm phases take place in the dawn sector. Arc event lifetimes and expectation times calculated for different substorm phases show that the longest arc-dominated periods are found during growth phases, while the longest arc waiting times occur during expansion phases. Most of the arc events end when arcs evolve to more complex structures. This is true for all substorm phases. Based on the number of images of auroral arcs and the durations of substorm phases, we conclude that a randomly selected auroral arc most likely belongs to a substorm expansion phase. A small time delay, of the order of a minute, is observed between the magnetic signature of the substorm onset (i.e., the beginning of the negative bay) and the auroral breakup (i.e., the growth phase arc changing into a dynamic display). The magnetic onset was observed to precede the structural change in the auroral display. A longer delay of a few minutes was found between the beginning of the growth phase and the first detected auroral structure.
机译：极光弧往往联系在一起磁安静的时间和亚暴增长阶段。在全球和当地的磁结构活动调查的出现率在不同级别的磁极光弧活动。磁强计所描述的条件从五磁力计——极光相机数据电离层雷达——全天相机大在芬兰和瑞典的实验拉普兰。从当地的扩张,和复苏阶段电喷流指数(IL)在1996 - 2007年和分析极光结构在不同阶段。在不同全球磁活动的水平,描述的行星Kp指数。极光的分布结构亚暴阶段和Kp水平是相似的形状。极光弧。发生在所有条件的主要元素极光。阶段发生在premidnight部门,虽然发生在至少arc-dominated亚暴阶段黎明部门。期望时间计算出不同亚暴阶段表明,最长的arc-dominated时期被发现在增长阶段,而弧最长等待时间发生在扩张阶段。结束时弧进化到更复杂的结构。这适用于所有亚暴阶段。极光弧和图像的数量亚暴阶段的持续时间,我们得出这样的结论:a随机选择的极光弧最有可能是亚暴扩张阶段。一分钟的延迟,订单的磁性签名之间的亚暴开始(即负湾)的开始和极光分手(即增长阶段弧改变成一个动态显示)。观察磁发作之前结构变化的极光。之间的时间延迟几分钟被发现增长的开始阶段和第一检测到极光结构。

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