Properties of 6300‐Å auroral emissions at South Pole
Properties of 6300‐Å auroral emissions at South Pole
复制标题
南极 6300-Å 极光发射的特性
DOI：
10.1029/ja094ia02p01402
复制
发表时间：
1989
影响因子：
--
通讯作者：
S. Mende
中科院分区：
文献类型：
--
作者：
R. Rairden;S. Mende
在1983年至1986年4月至8月的南方冬季，利用位于南极站的图像增强全天照相机记录了极地帽区的光学（6300 A）观测。在这些全天图像中看到的极光结构与子午线狭缝（keogram）成像仪记录的特征相关联。光阑图提供了对极光活动的方便调查，但是为了确定与通常观测到的光阑图轨迹相关的精确极光形态，需要全天图像。给出了极光活动在日周期周围的典型图像。在上午和下午（当地磁时），通常可以看到极光椭圆穿过天顶，并且频繁的经向运动出现在kegraph上。在正午期间，离散的向极地移动的弧偶尔出现，可能与通量转移事件或等离子体流型的类似变化有关。夜侧角图显示了与太阳对齐的弧的特征特征，这在相关的全天空图像中得到了很好的定义。三分之二对准太阳的弧线是在当地午夜的黎明观测到的。相对于一个面向太阳的非旋转框架，这些弧线以通常小于250米/秒的速度在头顶漂移。没有明显的偏好显示为向东（朝东）或西向（朝西）漂移方向。这些与太阳对齐的弧线发生的频率比以前认为的要高：我们在219个日间图像收集期间共观察到114次这样的事件。现有的行星际磁场测量虽然有限，但表明三分之二的太阳对准弧的Bz≥0。虽然By与它们的地方时分布没有相关性，但有迹象表明，By < 0时优先出现向黎明运动，而By < 0时优先出现向黄昏运动。
Optical (6300 A) observations of the polar cap region were recorded during the April to August austral winters of 1983 through 1986 with an image-intensified all-sky camera located at South Pole Station. Auroral structures seen in these all-sky images are correlated with the signatures registered by a meridian slit (keogram) imager. The keograms provide a convenient survey of auroral activity, but the all-sky images are required in order to determine the precise auroral morphology associated with the commonly observed keogram traces. Typical images of auroral activity around the diurnal period are presented. During morning and afternoon (magnetic local time) the auroral oval is usually seen crossing zenith, and frequent meridional movements appear on the keograms. During the midday interval, discrete poleward moving arcs occasionally appear, likely associated with flux transfer events or similar changes in the plasma flow pattern. Nightside keograms show the characteristic signatures of Sun-aligned arcs, which are well defined in the associated all-sky images. Two thirds of the Sun-aligned arcs are observed on the dawnside of local midnight. The arcs drift overhead at velocities of typically less than 250 m/s with reference to a Sun-oriented noncorotating frame. No significant preference is shown for easterly (dawnward) or westerly (duskward) drift directions. These Sun-aligned arcs occur with greater frequency than previously thought: we observe a total of 114 such events during 219 diurnal periods of image collection. The available interplanetary magnetic field measurements, though limited, indicate Bz ≥ 0 for two thirds of the Sun-aligned arcs. While no correlation is found between By and their local time distribution, there is a suggestion that dawnward motions appear preferentially with By > 0 and duskward motions with By < 0.