Interhemispheric asymmetries in the occurrence of magnetically conjugate sub-auroral polarisation streams
Interhemispheric asymmetries in the occurrence of magnetically conjugate sub-auroral polarisation streams
复制标题
磁共轭亚极光偏振流发生时的半球不对称
DOI：
10.5194/angeo-23-1371-2005
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发表时间：
2005
影响因子：
1.9
通讯作者：
T. Kikuchi
中科院分区：
文献类型：
--
作者：
M. Parkinson;M. Pinnock;J. Wild;M. Lester;T. Yeoman;S. Milan;H. Ye;J. Devlin;H. Frey;T. Kikuchi
抽象的。高能离子和电子向地球的注入标志着磁层亚暴的开始。在内磁层(L 4)，高能离子向西漂移，电子向东漂移，从而增强赤道环电流。波与粒子的相互作用可以加速这些粒子向辐射带辐射能量。在午夜前，离子被注入到离地球略近的区域，导致在内部磁层形成径向极化场。这张图显示的是电离层极光椭圆形赤道方向的极地电场。极地电场随后被电离层反馈放大，从而产生极光西向流动通道(AWFC)。就电场强度而言，AWFC是电离层中亚暴的最强表现形式。因为地磁通量管本质上是等位势的，所以应该在北半球和南半球同时观察到类似的AWFC信号。在这里，我们介绍了在2002年11月30日晚上的两个亚暴期间，包括多个起始点，在午夜前区域观测到的AWFC活动的磁共轭SuperDARN雷达观测。北半球的观测是用位于阿拉斯加州萨蒙王(57)的日本雷达进行的，南半球的观测是用位于塔斯马尼亚州布鲁尼岛的塔斯曼国际地球空间环境雷达(TIGER)(55。LANL对高能离子和电子通量的地球同步卫星观测监测了内磁层亚暴的影响(L，6)。雷达观测到的AWFC活动与在地球同步轨道上观测到的活动以及使用地面磁力计观测到的电离层向西的电流浪涌相吻合。AWFC相对于极光椭圆形的位置是从成像航天器上记录的FUV极光图像推断出来的。DMSP SSIES离子漂移测量证实了极光椭圆形赤道方向存在AWFCs。AWFC半球间信号的系统不对称性可能是因为在靠近亚暴偶极化区的L壳层上磁通量管发生了扭曲。暂态不对称性归因于附近场向电位降和电流的发展。
Abstract. Earthward injections of energetic ions and electrons mark the onset of magnetospheric substorms. In the inner magnetosphere (L 4), the energetic ions drift westward and the electrons eastward, thereby enhancing the equatorial ring current. Wave-particle interactions can accelerate these particles to radiation belt energies. The ions are injected slightly closer to Earth in the pre-midnight sector, leading to the formation of a radial polarisation field in the inner magnetosphere. This maps to a poleward electric field just equatorward of the auroral oval in the ionosphere. The poleward electric field is subsequently amplified by ionospheric feedback, thereby producing auroral westward flow channels (AWFCs). In terms of electric field strength, AWFCs are the strongest manifestation of substorms in the ionosphere. Because geomagnetic flux tubes are essentially equi-potentials, similar AWFC signatures should be observed simultaneously in the Northern and Southern Hemispheres. Here we present magnetically conjugate SuperDARN radar observations of AWFC activity observed in the pre-midnight sector during two substorm intervals including multiple onsets during the evening of 30 November 2002. The Northern Hemisphere observations were made with the Japanese radar located at King Salmon, Alaska (57 , and the Southern Hemisphere observations with the Tasman International Geospace Environment Radar (TIGER) located at Bruny Island, Tasmania ( 55 . LANL geosynchronous satellite observations of energetic ion and electron fluxes monitored the effects of substorms in the inner magnetosphere (L 6). The radar-observed AWFC activity was coincident with activity observed at geosynchronous orbit, as well as westward current surges in the ionosphere observed using ground-based magnetometers. The location of AWFCs with respect to the auroral oval was inferred from FUV auroral images recorded on board the IMAGE spacecraft. DMSP SSIES ion drift measurements confirmed the presence of AWFCs equatorward of the auroral oval. Systematic asymmetries in the interhemispheric signatures of the AWFCs probably arose because the magnetic flux tubes were distorted at L shells passing close to the substorm dipolarisation region. Transient asymmetries were attributed to the development of nearby field-aligned potential drops and currents.