Aurora conjugacy during substorms: Coordinated Antarctic ground and Polar Ultraviolet observations
Aurora conjugacy during substorms: Coordinated Antarctic ground and Polar Ultraviolet observations
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亚暴期间的极光共轭：协调南极地面和极地紫外线观测
DOI：
10.1029/2001ja900025
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发表时间：
2001
期刊：
影响因子：
--
通讯作者：
C. Meng
中科院分区：
文献类型：
--
作者：
V. Vorobjev;O. Yagodkina;D. Sibeck;K. Liou;C. Meng
利用南极米尔尼站(Φ‘=−77.4°校正地磁纬度)的同时光学观测和极地卫星拍摄的北极光椭圆形紫外线成像仪图像，确定了包括极光亚暴在内的10个时间间隔(1.5至3小时)北半球夜间极光相对于南半球夜侧极光的位移。极光凸起极地边缘的位移可能很大，在CGL中最高可达50。位移的感觉和大小与两个半球的偶极子倾角或电离层电导率的不同无关，而与黄道面上的行星际磁场(IMF)方向有关。当Bx>；0和Bx>；0时，极光在北半球达到较高纬度，但在南半球，当Bx>；0和Bx>；0时，极光出现在较高纬度。共轭地面磁强计的扰动也表现出类似的不对称性。相比之下，当IMF强度较弱、IMF取向波动或IMF具有垂直螺旋取向时，极光的位移较小。即使在纬度相似的情况下，局部明亮的极光形式和瞬变增强往往只发生在一个半球。我们的结果证明了IMF的赤道分量有效地穿透到了磁层。
Simultaneous optical observations at the Antarctic station Mirny (Φ′= −77.4° Corrected geomagnetic latitude (CGL)) and Ultraviolet Imager images of the northern auroral oval from the POLAR satellite were used to determine the displacement of nightside aurorae in the Northern Hemisphere relative to those in the Southern Hemisphere during 10 (1.5 to 3 hour long) time intervals including auroral substorms. Displacements of the poleward edge of the auroral bulge can be significant, up to 50 in CGL. The sense and magnitude of displacements are not related to the dipole tilt angle or differing ionospheric conductivity in the two hemispheres but rather to interplanetary magnetic field (IMF) orientations in the ecliptic plane. Aurorae reach higher latitudes in the Northern Hemisphere when Bx<0 and By>0 but occur at higher latitudes in the Southern Hemisphere when Bx>0 and By<0. Perturbations in conjugate ground magnetometers display a similar asymmetry. By contrast, displacements of the aurora are small when the IMF strength is weak, the IMF orientation fluctuates, or the IMF has an orthospiral orientation. Even when the latitudes are similar, local bright auroral forms and transient intensifications often occur in only one hemisphere. Our results testify to the effective penetration of the equatorial component of the IMF into the magnetosphere.