Quasi-periodic rapid motion of pulsating auroras
Quasi-periodic rapid motion of pulsating auroras
复制标题
脉动极光的准周期快速运动
DOI：
10.1016/j.polar.2016.03.005
复制
发表时间：
2016
期刊：
影响因子：
1.8
通讯作者：
Naomoto Iwagami
中科院分区：
文献类型：
--
作者：
Yoko Fukuda;Ryuho Kataoka;Yoshizumi Miyoshi;Yuto Katoh;Takanori Nishiyama;Kazuo Shiokawa;Yusuke Ebihara;Donald Hampton;Naomoto Iwagami
我们报告了与嵌入在主脉动中的所谓3 ± 1 Hz调制相关的脉动极光的快速运动。在脉动开启阶段，经常在脉动斑块的边缘周围观察到重复性扩张。有些事件显示出一些脱离的膨胀远离主要的变形脉动斑块。在电离层高度，大约80%的膨胀速度小于70 km s− 1，这小于从磁层赤道到电离层的阿尔文速度。速度为数十km/s− 1的快速运动不太可能用斜向传播的合唱元素来解释，因为斜向合唱波的垂直速度高于阿尔文速度，而斜向传播的合唱元素已知会引起3 ± 1 Hz的调制。我们讨论了慢模阿尔文波作为候选调制源产生的快速运动。一些速度超过150 km s-1的非重复膨胀事件也出现在ON阶段的开始。这些非重复性扩张运动的特征在于与重复性扩张运动相比的长位移。膨胀速度的差异表明斑块运动的不同形成机制。
We report rapid motion of pulsating auroras associated with so called 3 ± 1 Hz modulations embedded in the main pulsations. During the pulsation ON phase, repetitive expansions are often observed around the edges of pulsating patches. Some events show a few detached expansions traveling away from the main deformed pulsating patch. Approximately 80% of all expansion speeds were found to be less than 70 km s−1at ionospheric altitudes, which is less than the projected Alfvén speed from the magnetospheric equator to the ionosphere. The rapid motions with speeds of tens of km s−1are unlikely to be explained by obliquely propagating chorus elements, which are known to cause the 3 ± 1 Hz modulation, because the perpendicular speed of the oblique chorus waves is higher than the Alfvén speed. We discuss the slow-mode Alfvén wave as a candidate modulation source to generate the rapid motions. A few non-repetitive expansion events with a speed of more than 150 km s−1also appear at the onset of the ON phase. These non-repetitive expanding motions are characterized by a long displacement compared to the repetitive expanding motions. The differences in the expansion speeds indicate different formation mechanisms of the patch motions.