We show four auroral initial brightening events at substorm onsets focusingon fine structures and their longitudinal dynamics, which were observed byall-sky TV cameras (30-Hz sampling) on January 2008, in Canada. For twoinitial brightenings started in the field of views of the cameras, we foundthat they started at longitudinal segments with a size of less than ~30–60 km.One brightening expanded with wavy structures and the otherexpanded as a straight arc. Although the two events had differentstructures, both brightening auroras expanded with an average speed of ~20 km/sin the first 10 s, and ~10 km/s in the following 10 s. Theother two events show that brightening auroras developed with periodicstructures, with longitudinal wavelengths of ~100–200 km. Assumingthat the brightening auroras are mapped to the physical processes occurringin the plasma sheet, we found that the scale size (30–60 km) and theexpanding speed (20 km/s) of brightening auroras correspond to the order ofion gyro radii (~500–1400 km) and Alfvén speed or fast ion-flowspeed (~400 km/s), respectively, in the plasma sheet.
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机译：我们在2008年1月在加拿大的全天候电视摄像机（30 Hz采样）观察到的次风暴中，聚焦于精细结构及其纵向动力学的四个极光初始增亮事件。对于从摄像机视野开始的两次增亮，我们发现它们始于纵向段，其大小小于30-60 km。一次增亮具有波浪形结构，而另一场则呈直线扩展。尽管这两个事件具有不同的结构，但增亮的极光均在最初的10 s内以〜20 km / s的平均速度扩展，在接下来的10 s内以〜10 km / s的平均速度扩展。另外两个事件表明，增亮的极光具有周期性结构，其纵向波长约为100-200 km。假设增亮的极光映射到等离子片中发生的物理过程，我们发现增亮的极光的规模大小（30–60 km）和扩展速度（20 km / s）与负离子陀螺半径（〜500– 1400 km）和等离子板中的Alfvén速度或快速离子流速度（〜400 km / s）。
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