Characteristics of the instantaneous auroral oval in the 1200–1800 MLT sector
Characteristics of the instantaneous auroral oval in the 1200–1800 MLT sector
复制标题
1200-1800 MLT扇区瞬时极光椭圆形特征
DOI：
10.1029/ja086ia09p07657
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发表时间：
1981
影响因子：
--
通讯作者：
C. Anger
中科院分区：
文献类型：
--
作者：
J. Murphree;L. Cogger;C. Anger
利用ISIS 2号卫星极光成像仪在3914a和5577a的二维光学图像，研究了下午扇区的极光特征。观测到的极光结构可以分为三种类型：漫射极光，孤立的离散极光，以及从下午到晚上连接的离散弧。漫射极光只有在行星际磁场的By分量为正且没有明显的亚暴过程（Bz通常为正，AE值较低）时才会观测到。当By为负且不依赖于亚暴的存在时，观察到孤立的离散特征。连接弧的范畴要求亚暴发生时伴有明显的西向电喷流。240 γ的平均声发射值比扩散或孤立类别高3倍。在次暴扩张阶段，这些连接弧与极光凸起以西的纬向西限制的电喷流相一致。
By using two-dimensional optical images at 3914 A and 5577 A from the ISIS 2 satellite auroral imager, we have investigated the characteristics of auroras in the afternoon sector. The observed auroral configurations can be placed into three categories: diffuse aurora only, isolated discrete aurora, and discrete arcs connecting from the afternoon to the evening sector. Diffuse aurora only is observed when the By component of the interplanetary magnetic field is positive and no substorm processes are evident (Bz normally positive and AE values low). Isolated discrete features are observed when By is negative and are not dependent upon the presence of a substorm. The connected arcs category requires a substorm to have occurred with a pronounced westward electrojet. The average AE value of 240 γ is a factor of 3 higher than for the diffuse or isolated categories. During the expansion phase of a substorm these connecting arcs are identified with the latitudinally confined westward electrojet to the west of the auroral bulge.