On the lifetime and extent of an auroral westward flow channel (AWFC) observed during a magnetospheric substorm
On the lifetime and extent of an auroral westward flow channel (AWFC) observed during a magnetospheric substorm
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关于磁层亚暴期间观测到的极光西向气流通道（AWFC）的寿命和范围
DOI：
10.5194/angeo-21-893-2003
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发表时间：
2003
影响因子：
1.9
通讯作者：
P. Ponomarenko
中科院分区：
文献类型：
--
作者：
M. Parkinson;M. Pinnock;H. Ye;M. Hairston;J. Devlin;P. Dyson;R. Morris;P. Ponomarenko
摘要。在麦夸里岛（-65°L）测得的地磁X分量-190 nt负湾表明，在2000年2月27日世界时09:58至11:10发生了一次电离层亚暴。利用塔斯曼国际地球空间环境雷达（TIGER）（一种南半球高频超级雷达）测量的后向散射功率、LOS多普勒速度和多普勒频谱宽度几乎同时观测到一个极光西流通道（AWFC）的特征。AWFC的许多特征与发生在极化急流（PJ）或亚极光离子漂移（SAID）事件期间的特征相似，表明它可能是一个充分发展的强烈西流通道的前兆，满足PJ/SAID的所有标准。波束摆动分析表明，与通道相关的向西漂移（极向电场）在时间和空间上都很有结构，但在22 min的次暴开始时间间隔09:56 ~ 10:18，平滑速度增长到~ 800 ms -1 （47 mVm -1）。在约5分钟的速度峰值期间，向西漂移的最大速度为>1.3 km s -1 (>77 mVm -1)，在扩展阶段的10:40 UT达到峰值。在6分钟的恢复阶段间隔（11:04至11:10 UT）内，漂移迅速衰减至~ 300 ms -1 （18 mVm -1）。总的来说，AWFC的寿命为74分钟，位于Harang不连续面以西-65°L附近的夜间扇区。大的西向漂移被限制在一个纵向延伸bbb20°（>1.3 h磁地方时）、纬向宽度~2°L的地理纬向通道内。在纬度约100 km的半宽处，峰值电势为bbb7.7 kV。然而，在恢复阶段结束时，进一步向极地观测到的瞬态速度为>3.1 km s -1，电位>18.4 kV。利用DMSP测量确定的极光椭圆边界表明，主要气流通道与弥散极光椭圆的赤道边界重叠。在流道后~ 2 h的时间间隔内，观测到一个~ 3°L宽的散射带向西缓慢漂移，速度逐渐衰减到~ 50 ms -1 （3 mVm -1）。观测到散射延伸过哈朗不连续，并具有主要电离层槽的多普勒特征，暗示了f区等离子体进一步耗尽的流动通道。这种散点特征与高纬度地区向东漂移的散点特征相反。关键字。电离层（极光电离层；电场和电流；电离层-磁层相互作用）磁层物理（风暴和亚风暴）
Abstract. A -190-nT negative bay in the geomagnetic X component measured at Macquarie Island ( -65° L ) showed that an ionospheric substorm occurred during 09:58 to 11:10 UT on 27 February 2000. Signatures of an auroral westward flow channel (AWFC) were observed nearly simultaneously in the backscatter power, LOS Doppler velocity, and Doppler spectral width measured using the Tasman International Geospace Environment Radar (TIGER), a Southern Hemisphere HF SuperDARN radar. Many of the characteristics of the AWFC were similar to those occurring during a polarisation jet (PJ), or subauroral ion drift (SAID) event, and suggest that it may have been a pre-cursor to a fully developed, intense westward flow channel satisfying all of the criteria defining a PJ/SAID. A beam-swinging analysis showed that the westward drifts (poleward electric field) associated with the flow channel were very structured in time and space, but the smoothed velocities grew to ~ 800 ms -1 (47 mVm -1 ) during the 22-min substorm onset interval 09:56 to 10:18 UT. Maximum west-ward drifts of >1.3 km s -1 (>77 mVm -1 ) occurred during a ~ 5-min velocity spike, peaking at 10:40 UT during the expansion phase. The drifts decayed rapidly to ~ 300 ms -1 (18 mVm -1 ) during the 6-min recovery phase interval, 11:04 to 11:10 UT. Overall, the AWFC had a lifetime of 74 min, and was located near -65° L in the evening sector west of the Harang discontinuity. The large westward drifts were confined to a geographic zonal channel of longitudinal ex-tent >20° (>1.3 h magnetic local time), and latitudinal width ~2° L . Using a half-width of ~ 100 km in latitude, the peak electric potential was >7.7 kV. However, a transient velocity of >3.1 km s -1 with potential >18.4 kV was observed further poleward at the end of the recovery phase. Auroral oval boundaries determined using DMSP measurements suggest the main flow channel overlapped the equatorward boundary of the diffuse auroral oval. During the ~ 2-h interval following the flow channel, an ~ 3° L wide band of scatter was observed drifting slowly toward the west, with speeds gradually decaying to ~ 50 ms -1 (3 mVm -1 ). The scatter was observed extending past the Harang discontinuity, and had Doppler signatures characteristic of the main ionospheric trough, implicating the flow channel in the further depletion of F-region plasma. The character of this scatter was in contrast with the character of the scatter drifting toward the east at higher latitude. Key words. Ionosphere (auroral ionosphere; electric fields and currents; ionosphere-magnetospehere interactions) Magnetospheric physics (storms and substorms)